Dissertations / Theses on the topic 'Fat composition'

Abstract Sheep fat contains relatively high levels of saturated fatty acids while poly-unsaturated fatty acids (PUFA) are toxic to cellulolytic bacteria and are also saturated in the rumen. Stabilization of residual oil in sunflower oilcake by conversion into calcium salts would be advantageous. Alpha lipoic acid acts as an anti-oxidant to ameliorate the effects of oxidative stress caused by high dietary levels of PUFA. Residual oil (14%) in mechanically extracted (expeller) sunflower oilcake (SFOC) was saponified in situ and compared in a complete feedlot diet (100 g crude protein and 31 g extractable fat/kg feed) with commercially extracted oilcake containing 2.4% residual oil (control diet with 29 g fat and 123 g crude protein kg feed) fed to four groups of 10 SA Mutton Merino weaner lambs (ca. 23 kg) for nine weeks. Both diets were fed either with, or without a weekly oral dosing of 500 mg α-lipoic acid. Fatty acid composition was determined on back fat samples while thiobarbituric acid-reactive substances (TBARS) were determined on samples of m. longissimus dorsi stored for zero and six months and displayed for six days. The back fat of the lambs on the saponified expeller SFOC diets contained significantly higher levels of saturated fatty acids and lower levels of mono-unsaturated fatty acids. PUFA were unaffected. High TBARS levels (>1.0) were found after six months storage. Non significant increases in TBARS were observed in the groups that received lipoic acid.

La tesi es compon de tres estudis que es van realitzar amb la finalitat de disminuir el cost analític que suposa la determinació rutinària de la greix intramuscular (GIM) i de l'àcid oleic, així com d’investigar els mecanismes biològics de la deposició del greix. En el primer estudi, es va desenvolupar un mètode analític d'alt rendiment per a la quantificació de l'àcid oleic en carn de porc, mitjançant un sistema d'anàlisi per injecció de flux basat en una espectrometria de masses amb ionització per electrosprai. El nou mètode, que permet una quantificació ràpida del contingut en àcid oleic en mostres petites, podria ser adequat per a la classificació de porcs i canals pel seu contingut en àcid oleic. El segon estudi, avalua l'ús d'indicadors lipídics en sèrum com biomarcadors precoços de la composició i contingut del GIM i del greix subcutani. Cap dels indicadors lipídics investigats es recomanen com un biomarcador precoç del greix. En l’últim estudi, es va examinar l'efecte de la selecció contra greix dorsal a GIM constant sobre el patró d'expressió proteica hepàtica i la composició d'àcids grassos en fetge, múscul i greix subcutani . Es conclou, que el patró d'expressió proteica hepàtica en porcs està afectat per la selecció contra greix dorsal
La tesis se compone de tres estudios que se realizaron con el fin de disminuir el coste analítico que supone la determinación rutinaria de la grasa intramuscular (GIM) y del ácido oleico, así cómo de investigar los mecanismos biológicos de la deposición de la grasa. En el primer estudio se desarrolló un método analítico de alto rendimiento para la cuantificación del ácido oleíco en carne de cerdo usando un sistema de análisis por inyección de flujo basado en una espectrometría de masas con ionización por electrospray. El nuevo método, el cual permite una cuantificación rápida del contenido en oleico en muestras pequeñas, podría ser adecuado para la clasificación de cerdos y canales por su contenido en oleico. El segundo estudio evalúa el uso de indicadores lipídicos en suero cómo biomarcadores de la composición y contenido de la GIM y la grasa subcutánea a edades tempranas. Ninguno de los indicadores lipídicos investigados se recomiendan que se usen cómo un biomarcador precoz de la grasa. El último estudio examinó el efecto de la selección contra grasa dorsal a constante GIM sobre la expresión proteíca hepática, y la composición de ácidos grasos en hígado, músculo y grasa subcutánea. Se concluye que el patrón de expresión proteíca hepática en cerdos es afectada por la selección contra grasa dorsal.
The thesis comprises of three studies, with the aim at decreasing the cost of routinely intramuscular fat (IMF) and acid oleic determinations, as well as investigating the biological mechanisms of fat deposition. In the first study, it was developed a high-throughput analytical method for oleic fatty acid quantification in pork using a flow injection analysis system based on electrospray ionisation mass spectrometry. The new method, which allows for a rapid quantification of oleic content in small pork samples, may be used as a suitable method for ranking pigs and carcasses by oleic content. The second study assesses the usefulness of serum lipid indicators as early biomarkers of IMF and subcutaneous fat content and composition. None of the serum lipid indicators investigated is recommended to be used as an early biomarker of fatness. The last study examined the effect of selection against backfat thickness at constant IMF on hepatic protein expression and fatty acid composition in liver, muscle, and subcutaneous fat. It is concluded that hepatic protein expression pattern in pigs is affected by selection for decreased backfat thickness.

La perception du gras chez l’homme est un phénomène complexe du fait de sa nature multi-sensorielle impliquant la perception de la texture, la perception aromatique mais également la perception gustative. Cette dernière a été suggérée après l’identification de récepteurs aux acides gras au niveau des bourgeons gustatifs. Par ailleurs, des études récentes ont montré que la sensibilité au gras est variable entre individus. Des facteurs génétiques ou environnementaux pourraient expliquer en partie cette variation interindividuelle. Cependant, la salive pourrait aussi jouer un rôle dans cette perception. En effet, elle contient des molécules capables d’interagir avec le gras comme la lipase et les lipocalines. C’est aussi un fluide complexe qui contient une large diversité de protéines et de métabolites. De plus, sa régulation est complexe et peut varier à la suite d’une stimulation. En effet, des études récentes ont montré que le protéome salivaire est modifié à la suite d’une stimulation par des molécules correspondant aux saveurs primaires. Dans ce contexte, l’objectif de ce travail était de déterminer dans un premier temps s’il existe des liens entre la composition salivaire et la sensibilité gustative à un acide gras libre: l’acide oléique. Le deuxième objectif était d’étudier les modifications de la composition salivaire à la suite d’une stimulation gustative par l’acide oléique. Pour ceci deux approches ont été utilisées: des approches ciblées (activité enzymatique, capacité antioxydante etc) et des approches non-ciblées (protéomique et métabolomique). Deux groupes de treize sujets (hyper et hyposensible au goût de l’acide oléique) ont été sélectionnés à partir d’un panel de 73 participants. Leur salive a été collectée au repos et après stimulation par l’acide oléique. Les résultats montrent que la composition de la salive au repos est liée à la sensibilité à l’acide oléique. En effet, des marqueurs liés à la perception du goût ont été identifiés au sein du groupe des hypersensibles (anhydrase carbonique, cystatines et zinc alpha 2 glycoprotéine), alors que des marqueurs pouvant indiquer une activité bactérienne élevée (acides organiques) ont été identifiés au sein du groupe des hyposensibles. Par ailleurs, la composition de la salive collectée après stimulation par l’acide oléique est également modifiée et ces modifications sont différentes pour les sujets hyper et hyposensibles à cette stimulation
Human fat perception has recently triggered particular interest as it was shown that it does not only involve aroma and texture perception but also taste perception. The latter was supported by the presence of free fatty acids (FFA) taste receptors on the tongue. Recent studies have shown that fat taste sensitivity is variable among individuals. This inter-individual variation could be linked to genetic or environmental factors. However, saliva could also play a role in this perception. The role of saliva in taste perception is increasingly recognized. Saliva contains molecules able of interacting with fat such as lipase and lipocalin. It is also a complex fluid which contains a large diversity of proteins and metabolites. Its regulation is also complex and its composition may vary after a sensory stimulation. Indeed, studies have shown that when giving primary taste stimulations, the whole salivary proteome is modified. Thus, the first aim of the present work was to use both targeted (enzymatic activity, antioxidant capacity etc) and untargeted approaches (proteomics and metabolomics) to identify links between taste sensitivity to a fatty acid, oleic acid, and the salivary composition. The second aim was to investigate whether the salivary composition is modified after an oral stimulation by oleic acid.Two groups of thirteen male subjects (highly and weakly sensitive to the taste of oleic acid) were selected from an initial panel of 73 healthy participants. Their whole saliva was collected in two ways; the first without stimulation in order to study the links between oral sensitivity to oleic acid and saliva composition and the second using a stimulation by the same fatty acid in order to study potential modifications of saliva composition depending on sensitivity. Results show that salivary composition is linked to oral fatty acid perception. Markers previously reported as associated to taste perception were determined in the highly sensitive group (carbonic anhydrase, Zinc Alpha 2 glycoprotein and cystatins) while markers (organic acids) indicating a higher bacterial load were identified in weakly sensitive group. Furthermore, results obtained after stimulation by oleic acid suggest that saliva composition is modified, which confirms its dynamic nature. As different modifications were observed for the highly and weakly sensitive group, our results suggest that saliva is not only modified after a stimulation but also depending on the sensitivity to that particular stimulation

The LeanScreenTM app uses photographs and touchscreen technology of an iPad or iPhone to estimate body composition using the Department of Defense (DoD) prediction equations that use cirumference measurements of the neck, abdomen, waist, and hips. The purpose of this study was to determine the validity and reliability of the LeanScreenTM app in 148 weight-stable adults (82 men, 66 women) who were normal weight, overweight, or obese as defined by body mass index. The percent body fat (%BF) of each subject was estimated during one visit using dual-energy x-ray absorptiometery (DXA) as the criterion measure, and three field methods: the LeanScreenTM app, manually measured circumferences, and an OMRON bioelectical impedance (BIA) device. The %BF of each subject was determined once using DXA. Each of two administrators assessed the %BF of each subject twice using the LeanScreenTM app, manually measured circumferences, and the OMRON BIA device. When using the LeanScreenTM app, administrators assessed body composition using photographs they had taken and the photographs taken by the other administrator. Validity was established by comparing estimates of %BF from the LeanScreenTM app, manually measured circumferences, and the OMRON BIA device to %BF values obtained from DXA. Inter- and intrarater reliability was determined using mutliple measurements taken by each of two administrators. The three field methods were compared to DXA using mixed model ANOVA and Bland-Altman analyses. Analysis of the data revealed that the LeanScreenTM app, manually measured circumferences, and the OMRON BIA device significantly underestimated (p < 0.05) the %BF determined by DXA by an average of -3.26 ± 3.57 %BF, -4.82 ± 3.45 %BF, and -8.45 ± 3.48 %BF, respectively. Limits of agreement (LOA) for the LeanScreenTM app (6.99 %BF), manually measured circumferences (6.76 %BF), and the OMRON BIA device (6.82 %BF) were large. Slopes of the line-of-best-fit through the data in the Bland-Altman plots indicate that bias of %BF estimates using the LeanScreenTM app (slope = 0.06; p = 0.008) and the OMRON BIA device (slope = 0.15; p < 0.0001) increased as %BF increased. For each method of assessment, minimal variance could be attributed to different administrators peforming the assessment and each administrator performing multiple assessments. All inter- and intrarater reliability coefficients of the LeanScreenTM app, manually measured circumferences, and OMRON BIA estimates of %BF exceeded 0.99. The results of this study indicate that all three field methods of body composition assessments were highly reliable, however, these field measures are not recommended for use in the assessments of %BF due to a significant bias and large limits of agreements.

OBJECTIVE: The main objective of the present study was to assess the association between varying amounts of strength training and insulin resistance. Another goal was to assess the influence of several potential confounding variables on the strength training and insulin resistance relationship. Lastly, the role of waist circumference, fat free mass, and body fat percentage on the association between strength training and insulin resistance was assessed. METHODS: This cross-sectional study included 6561 randomly selected men and women in the US. Data were collected using the precise protocol established by NHANES. HOMA-IR was used as the outcome variable. Both time spent strength training and frequency of strength training bouts were used as exposure variables. RESULTS: There was not a statistically significant relationship between strength training and insulin resistance in women. However, after controlling for 10 potential confounding variables, men who reported no strength training had significantly higher levels of HOMA-IR compared to men who reported moderate or high levels of strength training (F = 9.87, P < 0.0001). Odds ratios were also assessed, and 10 potential confounding variables were controlled. Men reporting no strength training had 2.42 times the odds of having insulin resistance compared to men reporting moderate levels of strength training (95% CI: 1.19 to 4.93). Similarly, men reporting no strength training had 2.50 times the odds of having insulin resistance compared to men reporting high levels of strength training (95% CI: 1.25 to 5.00). CONCLUSION: There was a strong relationship between strength training and insulin resistance in US men, but not in US women. Differences in waist circumference, fat free mass, and body fat percentage, as well as demographic and lifestyle measures, do not appear to mediate the relationship.

Aquesta tesi doctoral forma part d'una línia de recerca sobre la millora genètica de la qualitat de la carn en porcí. Un dels recents objectius inclòs en algunes línies paternes seleccionades per mercats de qualitat és aconseguir un nivell òptim de greix intramuscular i de composició en àcids grassos sense penalitzar el rendiment magre. Aquesta tesi està formada per quatre estudis realitzats en una línia pura de porcs Duroc destinats a la producció de càrnics d'alta qualitat. Els estudis es van dissenyar amb l'objectiu d'entendre millor la variabilitat genètica subjactent al contingut de greix i a la composició en àcids grassos i d’identificar marcadors potencials a la selecció. El primer estudi va examinar els paràmetres genètics de la ruta de l'àcid linoleic (C18:2) a l'àcid araquidònic (C20:4). En particular, es va demostrar que s’espera que la selecció pel valor absolut de C18:2 proporcioni una resposta a la selecció similar a la selecció pel greix intramuscular a greix dorsal restringit. Aquests resultats van conduir a investigar el gen de la desaturasa-2 dels àcids grassos (FADS2), com a gen candidat per a la ruta metabòlica de C18:2. Així, el segon estudi va avaluar els efectes d'una variant (el polimorfisme rs321384923 es va utilitzar com a marcador) al promotor del gen FADS2. Els resultats van demostrar que aquest polimorfisme afecta el perfil d'àcids grassos n-6 millorant l'eficiència de desaturació de C18:2 a C20:4. Addicionalment, es va avaluar l'associació dels gens de les perilipines (PLIN) i del gen de la proteína d’unió al guanilat 1 (GBP1) amb caràcters de creixement i de qualitat de la carn. Així, el tercer estudi va examinar els efectes de dos polimorfismes als gens PLIN1 i PLIN2, relacionats amb l'emmagatzematge i la mobilització de lípids. Els resultats indiquen que el polimorfisme rs333231747 a PLIN2 està associat al creixement primerenc i al pes magre. L'últim estudi va demostrar que GBP1 té dos senyals de poliadenilació actius i que el seu ús depèn del genotip rs80800372. Els porcs portadors de l'al·lel G, associat a una menor viremia després de la infecció pel virus reproductiu i respiratori porcí, van tenir transcripcions més llargues i una menor expressió gènica. En condicions no epidèmiques, l'al·lel G va augmentar el contingut de greix intramuscular, però va disminuir el pes magre. El contingut de C18:2 i els marcadors genètics investigats es poden utilitzar per dissenyar estratègies de selecció adequades per millorar la qualitat de la carn i el creixement magre.
Esta tesis doctoral es parte de una línea de investigación sobre la mejora genética de la calidad de la carne en porcino. Uno de los recientes objetivos incluido en algunas líneas paternas seleccionadas para mercados de calidad es lograr un nivel óptimo de grasa intramuscular y de composición en ácidos grasos sin penalizar el crecimiento magro. Esta tesis comprende cuatro estudios realizados en una línea pura de cerdos Duroc destinados a la producción de cárnicos de alta calidad. Los experimentos se diseñaron con el objetivo de comprender mejor la variabilidad genética subyacente en el contenido de grasa y la composición en ácidos grasos e identificar marcadores potenciales a la selección. El primer estudio examinó los parámetros genéticos de la ruta del ácido linoleico (C18:2) al ácido araquidónico (C20:4). En particular, se demostró que se espera que la selección del valor absoluto de C18:2 proporcione una respuesta similar a la selección por grasa intramuscular a grasa dorsal restringida. Estos hallazgos llevaron a investigar el gen de la desaturasa-2 de los ácidos grasos (FADS2), como gen candidato para la ruta del C18:2. Por lo tanto, el segundo estudio evaluó los efectos de una variante (el polimorfismo rs321384923 se usó como marcador) en el promotor del gen FADS2. Los resultados mostraron que este polimorfismo afecta el perfil de ácidos grasos n-6 al aumentar la eficiencia de desaturación de C18:2 a C20:4. Además, se evaluó la asociación de los genes de las perilipinas (PLIN) y el gen de la proteína de unión a guanilato 1 (GBP1) con caracteres de crecimiento y de calidad de la carne. De este modo, el tercer estudio examinó los efectos de dos polimorfismos en PLIN1 y PLIN2, relacionados con la deposición y la movilización de lípidos. Los resultados indicaron que el polimorfismo rs333231747 en PLIN2 se asocia con el crecimiento temprano y con el peso magro. El último estudio mostró que GBP1 tiene dos señales de poliadenilación activas y que su uso depende del genotipo rs80800372. Los cerdos portadores del alelo G, asociado con una menor viremia después de la infección por el virus reproductivo y respiratorio porcino, tenían transcritos más largos y una menor expresión génica. En condiciones no epidémicas, el alelo G aumentó el contenido de grasa intramuscular pero disminuyó el peso magro. El contenido de C18:2 y los marcadores genéticos investigados se pueden usar para diseñar estrategias de selección adecuadas para mejorar la calidad de la carne y el crecimiento magro.
This PhD dissertation is part of a research line on the genetic improvement of pork quality. One of the latest goals to be included in some sire lines selected for premium markets is to achieve an optimum level of intramuscular fat and fatty acid composition without penalizing lean growth performance. This thesis is comprised of four studies conducted on a purebred Duroc line used for producing high-quality meat products. The experiments were designed with the aim to better understand the genetic variability underlying fat content and fatty acid compostion and to identify potential markers for breeding. The first study examined the genetic parameters of the linoleic acid (C18:2) to arachidonic acid (C20:4) pathway. In particular, it was showed that selection for the absolute value of C18:2 is expected to deliver a similar response outcome as selection for intramuscular fat at restrained backfat thickness. These findings led to investigate the fatty acid desaturase-2 (FADS2) gene, as a candidate gene for C18:2 metabolism route. Thus, the second study evaluated the effects of a variant (rs321384923 was used as a tag single nucleotide polymorphism) in the promoter of the FADS2 gene. Results showed that this polymorphism affects the n-6 fatty acid profile by enhancing the desaturation efficiency of C18:2 to C20:4. Additionally, the association of perilipin (PLIN) genes and guanylate-binding protein-1 (GBP1) gene with growth and meat quality traits was assessed. Thus, the third study examined the effects of two polymorphisms in PLIN1 and PLIN2, which have been related to lipid storage and mobilization. Results indicated that the rs333231747 polymorphism on PLIN2 is associated to early growth and lean weight. The last study showed that GBP1 has two active polyadenylation signals and that their usage depends on the rs80800372 genotype. The pigs carrying the G allele, which has been associated with lower viraemia after porcine reproductive and respiratory virus infection, had longer transcripts and lower gene expression. In non-epidemic conditions, the G allele increased intramuscular fat content but decreased lean weight. Linoleic acid content and the investigated genetic markers can be used to design appropriate selection strategies to enhance meat quality and lean growth.

Minimising variability in carcass quality to better meet market specifications is a priority for Australian pig producers, however issues with variability in carcass fat distribution have recently been raised, particularly in the belly primal. There has been a rapid increase in the use of low-cost, deep-litter (DL) housing systems in Australia over the past 15 years for rearing pigs. The inherent differences between the physical, thermal, and social environments of conventional (C) and DL production systems may well alter the growth path of the pig and subsequently alter fat metabolism and hence fat deposition and distribution. The general industry view is that pigs finished in DL housing are fatter and grow less efficiently than pigs finished in C housing, however contrasting carcass and growth performance results have been reported between housing systems. It is likely that the different housing environments affect the maintenance energy requirements of the growing pig, thereby affecting the availability of substrates for fat deposition and/or the requirements for fat mobilisation. Hence, raising pigs in C and/or DL production systems was identified as a likely contributor to variability in carcass fat distribution via the effects of the disparate environments on fat metabolism. The overall purpose of this thesis was to establish the effect of keeping pigs in C and/or DL housing systems on fat metabolism, and therefore fat deposition in the growing pig and fat distribution in the finished carcass. Industry considers that finishing pigs in C facilities allows greater flexibility in feeding and marketing decisions, allowing growth efficiency and backfat to be managed more effectively than in a DL system. Therefore an aspect of this thesis was to also examine the effects of an alternative management strategy, raising pigs in a combination of DL and C housing, on growth performance and fat deposition and distribution in the carcass. The presence of straw bedding is a major difference between C and DL housing systems. This was identified as a probable contributor to the differences in growth performance and carcass fat distribution found between pigs raised in the different housing systems, via its thermal properties and/or the ingestion of the straw on pig growth. Experiment 1a and 1b were designed to test the hypothesis that the growth path differs for pigs raised in C and DL housing systems, affecting biochemical indicators of fat metabolism and therefore fat accretion and distribution in the carcass. The study was conducted as a serial slaughter of pigs housed in C and DL systems allowing the pattern of fat accretion, and therefore the distribution of fat in the carcass, to be determined from 15¨C185 kg live weight (LW). The results confirmed the hypothesis that the growth path, fat accretion and fat distribution in the carcass differed for pigs raised in C and DL housing systems. In Experiment 1a, elevated lipogenic enzyme activities, higher percentages of saturated fatty acids (SFA) and higher concentrations of plasma glucose and lactate indicated lipogenesis was elevated in C pigs to 13 weeks of age, compared to young DL pigs, suggesting that fat accretion was higher in young C pigs. At 24 weeks of age however there was a shift in lipogenic enzyme activities, the percentage of SFA in backfat and the concentration of plasma glucose were higher in DL-housed pigs than C-housed pigs, indicating higher rates of lipogenesis. Elevated concentrations of plasma non-esterified fatty acids (NEFA) and glycerol in DL pigs indicated that lipolysis, or fat mobilisation, was higher in DL-housed pigs for the entire growth period. The results from Experiment 1b clearly indicated that during early growth, C pigs grew faster than DL pigs (0.71 vs 0.66 kg/day, P¡Ü0.05) and were heavier between 8-23 weeks of age (P¡Ü0.05). Therefore in conjunction with the results of Experiment 1a, it was expected that young C pigs would be fatter than DL pigs of the same age. However, dissection indicated no treatment differences in total carcass composition, although there was an effect of housing on carcass fat distribution with a trend (P=0.087) for a lower ratio of fat:lean in the belly primal of DL pigs compared to C pigs at 13 weeks of age. After 20 weeks of age however, growth rates were similar for pigs in both housing treatments and by 26 weeks of age there were no treatment differences in live weight (LW) but the rate of fat accretion in DL pigs, particularly in the loin and belly primals, increased rapidly. Differences in the thermal environments of C and DL housing, and therefore differences in the energy demand for thermoregulation, were likely to have contributed to the differences measured in lipogenesis, growth performance and carcass fat distribution. Experiment 2a and 2b tested the hypothesis that moving pigs from DL to C housing for finishing would improve overall growth performance and reduce carcass fatness compared to pigs raised in wean-to-finish DL housing. The biochemical measurements indicated few differences in the rate of lipogenesis between 13-week-old C and DL pigs. However, and in agreement with the findings from Experiment 1a, elevated plasma NEFA concentrations in DL pigs suggested higher rates of lipolysis. Up to 13 weeks of age, pigs in the DL housing system grew faster than C pigs, however similar to the findings of Experiment 1b, DL pigs were less efficient. In addition, P2 backfat depth was less in DL pigs, indicating they were leaner than C pigs, and though not reflected in total carcass composition, again there was an effect of housing on fat distribution. The move to an unfamiliar housing environment affected growth performance, reduced enzyme activity in backfat and the ratio of SFA in belly fat, suggesting these pigs had lower rates of lipogenesis. However in contrast to Experiment 1a, where lipogenesis was higher in older DL pigs compared to older C pigs, pigs finished in the DL housing had a trend for lower enzyme activity in belly fat (P=0.063), suggesting lower rates of lipogenesis, and higher plasma glycerol concentrations, suggesting a higher level of lipolysis compared to C-finished pigs. The carcass composition data (Experiment 2b) found that though there were no differences indicated by differences in P2 depth, there was a strong trend (P=0.057) for DL-finished pigs to have 2-6% less fat in the carcass as a result of significantly less fat in the shoulder (15% vs 17%) and belly (29% vs 33%) primals compared to C-finished pigs. The difference in belly primal composition was a reflection of the lower enzyme activities in belly fat and higher plasma glycerol concentrations in DL finished pigs. The results suggest that the type of housing during the finishing growth period has a greater impact on fat accretion and carcass composition than the type of housing during the grower period, or changing housing environment during growth. However, changing housing environment at 13 weeks of age affected growth, where there was a temporary reduction in daily LW gain, and therefore significantly lower (P¡Ü0.001) LW at slaughter (117 kg LW), compared to pigs that had remained in C or DL housing from wean-to-finish (123 kg LW). Moving pigs from DL to C housing to control carcass fat and improve growth performance compared to pigs grown wean-to-finish in DL housing, was not successful, and had a negative impact on performance and carcass quality by reducing growth efficiency and LW and increasing carcass fatness. The results also showed that contrary to the industry view that DL raised pigs are fatter, pigs in this experiment finished in DL housing had a lower fat:lean ratio in the carcass than pigs finished in the C system (P¡Ü0.05). The effects of straw on growth performance and carcass composition were evaluated in Experiment 3a and 3b by including straw in the grower and finisher diets (St+) and/or providing straw bedding (Bed+) to C-housed pigs. The experiment tested the hypothesis that the presence of straw alters the growth paths of pigs, affecting fat distribution in the carcass. Straw, as bedding and in the diet, affected pig growth paths and altered carcass fat distribution and, consistent with the findings for DL pigs in Experiments 1b and 2b, there was a trend for pigs with access to straw to have less fat in the belly (P=0.072). Elevated activity of key enzymes involved in lipogenesis, measured in Experiment 3a in belly fat and backfat from pigs fed the St+ diet, and a higher ratio of SFA in belly fat of pigs housed on concrete without straw bedding, suggested that in this experiment straw ingestion increased lipogenesis in belly fat and backfat of the growing pig, whilst straw bedding reduced lipogenesis in belly fat. Experiment 3b demonstrated an additive effect of straw on growth where average LW at slaughter for pigs without access to straw was significantly lower (110 kg), compared to pigs with access to one source of straw either via the diet or bedding (115 and 114 kg LW respectively), and pigs that had two sources of straw available (119 kg LW) (P¡Ü0.05). Although LW differed between treatments there were no differences in total carcass fat (P>0.10), yet there was an effect of straw on fat distribution. Pigs with access to straw had a lower ratio of fat and a higher ratio of lean tissue in the belly primal (P=0.072) compared to pigs that did not have straw. The effect of straw ingestion on lipogenesis and fat deposition may have occurred via the effects of dietary fibre (DF) on the dilution of dietary energy density. Pigs were able to compensate for the energy/nutrient dilution by increasing VFI and therefore growth was not affected, however fat acts as an insulator, and localised differences in fat distribution may have been related to increased heat production (HP) from the digestion of greater volumes of feed. In response, fat deposition may have been directed away from the belly location in order to facilitate heat loss. Floor type may have also affected fat distribution via differences in thermal conductivity. Straw has a lower thermal conductivity than concrete, hence pigs housed on concrete flooring may have a greater requirement for fat in the belly to reduce conductive heat loss. Results from Experiment 3a and 3b provided evidence that pigs housed on bedding consume straw in sufficient quantities. Pigs fed the straw diet had significantly higher concentrations of plasma acetate than pigs fed the control diet (P¡Ü0.001), and there was a trend for pigs housed on straw bedding to have higher levels than pigs without access to straw. An increase in plasma acetate can indicate increased microbial activity in gut, which occurs in response to higher levels of DF. In addition, pigs bedded on straw had higher gastrointestinal tract weights, which can also indicate higher levels of DF intake. Regression analyses of data across experiments showed that P2 backfat depth, the primary carcass composition prediction tool, accounted for less than 50% of the variation in percent carcass fat (R2=0.41). Furthermore, across experiments, P2 accounted for very little of the variability in percent belly fat (R2=0.01). These results highlight the inconsistency of P2 depth as a reliable indicator of carcass composition and the need for the development of additional criteria to be used in the selection of carcasses for specific markets as the composition of the belly primal was not indicated by the current carcass measurement system. From the results obtained in this thesis, it was proposed that: 1) The growth path of pigs is altered by the housing system in which they are reared and the more variable ambient temperature of the DL housing system would increase the energy requirement of young pigs for thermoregulation. As a consequence of the altered growth paths, fat metabolism differs for pigs raised in DL and C production systems. Lower rates of lipogenesis may occur in young DL pigs compared to C pigs and this can change as pigs grow, however fat mobilisation remains higher in DL pigs during growth. 2) Differences in the rate of lipogenesis, indicated by the biochemical measures, were generally not reflected in total carcass composition, however there were differences in carcass fat distribution where pigs raised in DL systems consistently had less fat in the belly primal. Rearing environment may provide an additional criterion when selecting carcasses for specific markets where variability in belly composition is an issue. 3) Pig raised in the DL environment are not always fatter than pigs housed in C facilities, and moving pigs from one housing environment to another during the growing-finishing period disrupts the growth path reducing growth performance and can increase carcass fatness. 4) Straw bedding, via ingestion and via its physical thermal properties, affects pig growth and fat distribution and may explain in-part the differences in pig growth performance and carcass quality found between C and DL housing systems.

Assessment of body fat percentage is desirable to identify health risks associated with obesity. There are few studies that have compared the assessment of body fat between air displacement plethysmography and dual-energy x-ray absorptiometry, particularly related to age and gender differences. The purpose of this study was to determine if body fat percent estimates differ depending on age and/or gender between air displacement plethysmography (Bod Pod, Life Measurements Instrument, Concord, CA) and dual-energy x-ray absorptiometry (DEXA, General Electric Medical Systems, Lunar Prodigy, Madison, WI). Sixty subjects were studied: 15 men and 15 women, 22-35 years and 15 men and 15 women, 55-80 years. Subjects were excluded if they competed in athletics or high-level exercise training in the last year. Standard calibration and testing procedures were used for both methods. Both methods were administered at least twice to evaluate reliability and were repeated a third time if the first two measures differed by >2%. Differences between methods for age groups and gender were analyzed using ANOVA and reliability comparisons between the body composition methods were evaluated with correlation coefficients and Bland-Altman plots. Using data for all subjects, DEXA (r = .996) and Bod Pod (r = .985) both showed good reliability. However, in younger females the reliability of the Bod Pod (r = .911) was lower. Sixteen of the 60 subjects required a third trial for the Bod Pod, whereas all repeated DEXA measures were consistent. The deviation between trial 1 and 2 for the DEXA (.6%) was significantly less than that in the Bod Pod (1.5%). Significant interactions between the body composition method and age group were found. Mean body fat percentage in the younger group was higher in the DEXA (24.1 + 1.1%) than the Bod Pod (23.0 + 1.3%) however, in the older group it was found to be lower in the DEXA (33.9 ± 1.1%) than the Bod Pod (37.2 ± 1.3%). Both the DEXA and the Bod Pod were reliable but repeated DEXA measures were more consistent than the Bod Pod measures. Bod Pod estimates of body fat percentage were lower for younger subjects, yet higher for older subjects compared to DEXA measurements.
School of Physical Education, Sport, and Exercise Science

We recently showed a critical role of Trpm5 in the transduction pathway for long chain polyunsaturated fatty acids. In the present study, I have begun to investigate dietary fat preference and the propensity to develop dietary-induced obesity in Trpm5-/- mice. My preliminary data shows that in male mice placed on a high fat diet, Trpm5-/- mice did not enhance their caloric intake as observed in wild type mice. Most surprisingly, however, was that I did not observe the same differences in between female mice, which posits a potential gender effect of this pathway on dietary fat intake. Also, I show that the preference for dietary fat is not disrupted in Trpm5-/- mice since there is no difference in dietary fat preference between Trpm5-/- and wild type mice. Wild type and Trpm5-/- mice both have a strong preference for the high fat diet, as demonstrated by the fact that they solely consumed the high fat diet. Consistent with our original hypothesis that these responses are specific for high fat feeding, I did not observe any differences in caloric intake in male mice on a high sucrose diet. Again, gender differences were observed, with Trpm5-/- female mice displaying a higher caloric intake than wild type female mice. Furthermore, I used a paired-feeding approach via oral gavage to delve further into whether the effect of Trpm5 disruption was due to pre- or post-ingestive effects. The results from this experiment show that all animals have a reduction in body weight and body fat with no significant difference between wild type and Trpm5-/- mice. This result suggests that the expression of Trpm5 in the oral cavity is necessary for the changes in body weight and composition observed during ad libitum feeding. Also, the fact that Trpm5-/- mice lost body weight and fat mass is contrary to our previous observations. When these animals consume the roughly same number of calories on a high fat diet ad libitum, we observe an increase in body weight and fat mass. This suggests that there might be another mechanism accountable for the response observed in Trpm5-/- mice when fed ad libitum. In conclusion, the results from these experiments suggest a link between dietary fat consumption and development of adiposity.

Menhaden oil, corn oil, olive oil or animal fat (1, 3, 5 or 8% of diet) effects on egg yolk fatty acids and hepatic lipogenic enzymes were studied in 35 week-old laying hens. Except for significantly lowered egg weights by menhaden oil, performance was unaffected. Yolk saturated fat remained constant (33-38% of yolk fat) regardless of fat source. Maximum o-3 fatty acid incorporation (.31 g/yolk) was reached with a deposition efficiency of 36.3% by feeding 5% menhaden oil. Yolk lipid contained.3% linolenic (C18:3o3), 1.0% eicosapentaenoic (C20:5o3), and 3.8% docosapentaenoic (C22: 5o3) acids. Maximum o-6 fatty acid incorporation (1.65 g/yolk) occurred with 17% efficiency when 8% corn oil was fed, primarily by increasing linoleic acid to 25.5%. Yolk oleate was inversely related to dietary linoleate. Only the highest menhaden oil levels significantly affected lipogenic enzymes: fatty acid synthetase and ATP citrate lyase (EC 4.1.3.8) activities were inhibited, while glucose-6-phosphate dehydrogenase (EC 1.1.1.49) activity was 2-3 times that of hens fed the basal diet. Malic enzyme (EC 1.1.1.40) activity was not significantly influence by dietary fat.

Sojourns at high altitude are often accompanied by weight loss and changes in body composition. The aim was to study body composition before and after 40 days high-altitude exposure. The subjects were four women and six men, non-smoking, healthy and active students and a scientist from Mid Sweden University in Östersund with a mean (SD) age of 26 (10) years. All subjects volunteered for a six-week trek to the Mount Everest Base Camp via Rolwaling in Nepal. Before the sojourn subject’s height was 177 (10) cm and weight was 71.9 (10) kg. Body composition was measured with Lunar iDXA at the Swedish Winter Sports Research Centre in Östersund before and after the trek. Total body mass (SD) decreased from 71.8 (10.0) kg before to 69.7 (9.4) kg after the trek (P=0.00). Total fat mass decreased from 14.7 (5.9) kg to 13.8 (4.6) kg (P=0.01). Fat percent decreased from 21.6 (7.9) % to 21.0 (7.2) % (P=0.03). Total lean mass decreased from 54.0 (10.0) kg to 52.9 (9.7) kg (P=0.01). Bone mineral content was unchanged, 3.04 (0.5) kg before and 3.03 (0.5) after (P=0.13). Thus both total body mass and total lean mass had decreased after a six week trekking in Nepal.

The objective of these studies was to design an optimal nutritional supplement suitable for grazing horses using fat and fiber to replace the grain and molasses in the traditional sweet feed. Thoroughbred mares and foals grazing bluegrass/clover pastures were used in these studies, twenty mares and their foals in 1994 to 1995, and twenty mares and foals in 1995 to 1996. Seasonal variation in pasture was examined, and the need for supplementation of nutrients and fibers was assessed. The nutritional status of grazing mares, foals, weanlings and yearlings, fed either a starch and sugar supplement (SS) or a fat and fiber supplement (FF), was examined using growth measurements, radiographic bone evaluations, milk composition and glucose tolerance tests. These studies suggest that fiber may be an important component of an ideal supplement for improved grass/legume pastures. Seasonal variation in pasture indicated an increase in hydrolyzable and rapidly fermed carbohydrates during periods of rapid growth. The FF supplement may have buffered seasonal changes and the increased hydrolyzable carbohydrate content in rapidly growing pasture, as evidenced by smoother growth curves in the yearlings. Young horses, after weaning until the following May, had lower estimated bone mineral content when fed the FF supplement. The lower bone mineral content in the FF supplemented horses may have been due to decreased absorption of calcium or metabolic and hormonal changes associated with adaptation to the different energy sources in the supplements. Milk composition of FF supplemented mares was influenced in ways likely to improve foal health. The FF supplemented mares had enhanced linoleic acid content, which may reduce the risk of gastric ulcers in foals, and increased immunoglobulin G concentration, which may enhance passive immunity. The carbohydrate status of mares, as assessed by glucose tolerance tests, indicated a slower glucose clearance that could be a metabolic adaptation of the mares to the SS and FF supplements.
Ph. D.

Les poudres laitières enrichies en matière grasse (MG) suscitent un intérêt croissant d'un point de vue économique et scientifique. Elle représentent une large gamme de produits, qui donnent lieu à de nombreues applications alimentaires parmi lesquelles les laits infantiles, les ingrédients laitiers, l'alimentation animale et les arômes encapsulés. La structure supramoléculaire de la MG dans les poudres enrichies en MG est souvent très complexe et mal connue. Elle confère à la MG des propriétés fonctionnelles de la matrice environnante. Malgré son intérêt, cette thématique n'a que peu été étudiée. De plus, le contrôle des propriétés physico-chimiques des poudres reste empirique dans le domaine industriel. Ainsi, il apparaissait primordial d'étudier les questions scientifiques en lien avec la structure supramoléculaire de la MG dans les poudres laitières, tant pour les communautés académiques qu'industrielles
Fat-filleddairy powders have acquired a growing interest from both an economical and a scientific point of view. They include a large variety of products for numerous food applications such as infant formulae, dairy ingredients, cattle feeding, and ecapsulated flavors. Fat supramolecular structure in fat-filled dairy powders can be very complex and is often poorly understood. It gives specific physicochemical properties to fat, which in turn gives specific functional properties to the surrounding matrix. Despite its interest, there was no exhaustive academic study of the topic at the beginning of this Ph. D. Program. Furthermore, controlling the physicochemical propoerties of these powders was still rather empirical in the industry. Hence, investigating the scientific issues related to fat supramolecular structure in fat-filled dairy powders appearead to be of primary importance for both the academic and industrial communities worldwide. The aims of this Ph. D. Research program were to investigate fat supramolecular structure and properties in fat-filled dairy powders in order (1) to determine adapted chemical compositions and process parameters to orientate fat supramolecular structure in fat-filled dairy powders, (2) to reach a better understanding of the mechanisms of the formation and evolution of fat supramolecular structure and fat physicochemical properties, and finally (3) to control powder physicochemical properties. The strategy was original as the study considered powders manufactured at the laboratory in controlled and industrial-like conditions and as specific methods for lipids were adapted to fat-filled dairy powders

The BOD POD (BP) is a device used for determining body composition that is based on the air displacement plethysmography method. There has been little research conducted on the BP, and the main focus of the research has been on the reliability and validity of the BP. Another important area of research with the BP is the effect that different types of clothing have on the percent fat readings from the BP. To produce the most accurate results, the manufacturers recommend that subjects wear a Lycra swimsuit, however this recommendation may not be feasible for some individuals or testing sites to follow. The purpose of this study was to determine if a standard type of clothing would affect the percent fat readings from the BP in a consistent manner. Fifty subjects (25 men, 25 women) of varying ages (19 to 84 years of age) and body composition (3.4 to 53.2% fat) completed six trials (3 cotton and 3 nylon) in the BP during one testing session. With the exception of the clothing, all other recommendations by the manufacturer were followed. The comparison between the two clothing conditions was analyzed with a 2-way ANOVA (gender x clothing), frequency distribution, and the Bland-Altman method. The reliability of the measurements was analyzed by comparing the absolute differences between the three trials with cotton clothing and the three trials with nylon clothing, with intra-class correlation coefficients, and the Bland-Altman method. The results from the 2-way ANOVA revealed that the interaction effect of gender and amount of clothing was significant with the difference between nylon versus cotton being 1.1% for men and 4.8% for women. There was also a significant difference between body fat measurements with the cotton clothing (24.2 + 11.2%) and the nylon clothing (27.1 + 11.6%) when analyzed with all the subjects combined (men and women). Reliability analysis resulted in intra-class correlation coefficients of 0.9 and 0.95 within the cotton and nylon clothing trials, respectively. The comparison of the absolute differences between the cotton trials and the nylon trials showed a between-trial standard deviation of approximately 0.6 for cotton and 0.7 for nylon. In the comparison of nylon to cotton clothing results, there was a greater difference between the results for the women than for the men. The men had a lower, similar difference when comparing the two clothing conditions, whereas the women had a higher, difference that was not similar between subjects. In conclusion, this study showed that using either cotton or nylon shorts for men is acceptable, whereas for women more testing is needed to find another type of clothing to replace the Lycra swimsuit that results in consistent percent fat measurements. Also, the reliability of the percent fat readings obtained with both clothing conditions was very good.
School of Physical Education

The aim of this thesis was to investigate the effects of dietary fatty acids on body composition and ectopic fat in humans, with emphasis on the role of the omega-6 polyunsaturated fatty acid (PUFA) linoleic acid (18:2n-6) and the saturated fatty acid (SFA) palmitic acid (16:0). The overall hypothesis was that linoleic acid would be beneficial compared with palmitic acid during overfeeding, as previously indicated in animals. Papers I, II and IV were double-blinded, randomized interventions in which different dietary fats were provided to participants and Paper III was a cross-sectional study in a community-based cohort (PIVUS) in which serum fatty acid composition was assessed as a biomarker of dietary fat intake. In Paper I, overfeeding with sunflower oil (n-6 PUFA) for 7 weeks caused less accumulation of liver fat, visceral fat and total body fat (as assessed by MRI) compared with palm oil (SFA) in young and lean subjects despite similar weight gain among groups. Instead, sunflower oil caused a larger accumulation of lean tissue. In Paper II, plasma from Paper I was analyzed with NMR-based metabolomics, aiming to identify metabolites differentially affected by the two dietary treatments. Acetate decreased by PUFA and increased by SFA whereas lactate increased by PUFA and decreased by SFA. In Paper III, the proportion of linoleic acid in serum was inversely associated with contents of visceral-, subcutaneous- and total body adipose tissue whereas the proportion of palmitic acid was directly associated with visceral- and total body adipose tissue in 70-year old men and women. In Paper IV, overfeeding with sunflower oil for 8 weeks caused less accumulation of liver fat compared with palm oil also in overweight and obese subjects. SFA increased visceral fat in men only. Accumulation of lean tissue was similar between groups. In conclusion, SFA (palmitic acid) from palm oil promotes marked liver fat accumulation in both normal-weight and overweight/obese subjects during overeating, whereas n-6 PUFA (linoleic acid) from sunflower oil prevents such liver fat accumulation. Diverging effects of SFA and PUFA on visceral adipose tissue and lean tissue may only be applicable in some groups and/or circumstances. These results imply that negative effects associated with weight gain (e.g. fatty liver) may be partly counteracted by the type fat in the diet, overall supporting a beneficial role of diets higher in unsaturated fat compared with saturated fat for preventing liver fat accumulation.

The objective of this investigation was to identify the appropriate isotopic fractionation factor for total body water (TBW) from ²H₂O enrichment in respiratory water vapor (RW) compared to serum (S), then to use the RW technique to estimate absolute TBW volumes and TBW relative to fat-free body mass (FFB) in three age groups (prepubescent, PP, age = 5-10 y; young adult, YA, age = 22-39 y; older adult, OA age = 65-84 y) of healthy white males and females. The effects of analytical technique (infrared spectrophotometry, IR versus isotope-ratio mass spectrometry, IRMS) and ambient relative humidity on estimates of TBW were also investigated. The composition of the FFB was estimated using a multi-component statistical model (body density, TBW and bone mineral density), and the errors associated with the traditional two-component formula for percent fat from body density were calculated. Our results demonstrated a significant (p < 0.0001) ²H₂O fractionation effect of 0.971 ± 0.005 (mean ± SEM, n = 36) for TBW from RW compared to S. Analysis by IR and IRMS were highly correlated (R² =.999) but IR values were significantly (p < 0.001) higher than IRMS. Deuterium enrichment in RW samples collected at ambient RH (∼20%) was significantly higher (Δ = 20.2 ± 4.5 ppm, mean ± SEM, p < 0.0005) than in RW samples collected at 100% RH, roughly equivalent to a 1.2 L (3.2%) difference in TBW. Total body water relative to FFB mass (W/FFB) was lower (p < 0.01) in YA males (71.0 ± 1.0%) and females (70.2 ± 1.3%) than in PP (boys = 73.1 ± 1.6%; girls = 72.2 ± 1.4%, mean ± SD). In OA, W/FFB was higher (p < 0.05) than in YA (OAM = 72.6 ± 1.1%; OAF = 72.2 ± 1.4%). The density of the FFB was 1.0996 and 1.0839 g/ml in OAM and OAF, respectively. Percent fat from density plus TBW and BMD was lower than from density alone in all groups but YA males, where it was 2.4 percent fat higher. In PP, the Siri density formula resulted in an overestimate of 5.8 ± 2.6 percent fat (mean ± SD, range = 1.4 to 13.6%). In OA females, the density formula overestimated percent fat by 4.4 ± 2.8% (range = 0 to 10.4%). In conclusion, RW corrected for isotopic fractionation will provide acceptable estimates of TBW, although the effects of analytical technique and RH should be controlled. The existence of age-related differences in FFB composition causes errors when the two-component model is used to estimate percent fat in PP and OA females.

Pig meat quality is determined by several parameters, such as lipid content, tenderness, water-holding capacity, pH, color and flavor, that affect consumers’ acceptance and technological properties of meat. Carcass quality parameters are important for the production of fresh and dry-cure high-quality products, in particular the fat deposition and the lean cut yield. The identification of genes and markers associated with meat and carcass quality traits is of prime interest, for the possibility of improving the traits by marker-assisted selection (MAS) schemes. Therefore, the aim of this thesis was to investigate seven candidate genes for meat and carcass quality traits in pigs. In particular, we focused on genes belonging to the family of the lipid droplet coat proteins perilipins (PLIN1 and PLIN2) and to the calpain/calpastatin system (CAST, CAPN1, CAPN3, CAPNS1) and on the gene encoding for PPARg-coactivator 1A (PPARGC1A). In general, the candidate genes investigation included the protein localization, the detection of polymorphisms, the association analysis with meat and carcass traits and the analysis of the expression level, in order to assess the involvement of the gene in pork quality. Some of the analyzed genes showed effects on various pork traits that are subject to selection in genetic improvement programs, suggesting a possible involvement of the genes in controlling the traits variability. In particular, significant association results have been obtained for PLIN2, CAST and PPARGC1A genes, that are worthwhile of further validation. The obtained results contribute to a better understanding of biological mechanisms important for pig production as well as for a possible use of pig as animal model for studies regarding obesity in humans.

The amount and composition of intramuscular fat (IMF) influence the sensory characteristics, nutritional value of beef and human health. The amount of fatty acid and its composition in beef varies by breed, nutrition, sex, age or carcass finishing level. The fat deposition and composition are determined by many genes that participate directly or indirectly in adipogenesis and lipid metabolism. The selection of animals with fat amount and composition suitable for the consumer is complex due to high cost of measurement, the moderate heritability and polygenic traits (many genes are involved with these traits). In the last decade with a great advance in bovine genomics resulted in the complete genome sequencing and the development of high-density chips of SNPs. This scientific advance jointly with technological improvement allowed the identification of genes responsible for important quantitative traits in cattle. This study aimed to identify and characterize genes associated with the deposition and composition of intramuscular fat in Nellore. A genome-wide association study (genome- wide association studies, GWAS) was performed to identify genomic regions associated with traits of interest and positional candidate genes. A total RNA sequencing (RNA-Seq) analysis was applied to transcriptome study of Longissimus dorsi muscle. Three hundred and eighty six Nellore steers were used for the evaluation of lipid content and fatty acid profile of LD, and genotyping with high-density chip SNP (SNP800 Illumina BeadChip). A subset of 14 animals, seven animals for each extremes of genomic estimated values (GEBV) were used to RNA-Seq analysis. Twenty-five genomic regions (1 MB window) were associated with the deposition and composition of intramuscular fat, which explained >= 1 % of the genetic variance. These regions were identified on chromosomes 2, 3, 6, 7, 8, 9, 10, 11, 12, 17, 26 and 27, many of these have not previously been found in other breeds and in these regions important genes were identified. Genomic regions and genes identified and presented here should be contribute to a better understanding of the genetic control of deposition and fat composition in beef cattle, and can be applied in breeding programs for animals that produce a quality and healthy beef to human consumers.
A quantidade e composição da gordura intramuscular (GIM) pode influenciar as características sensoriais, o valor nutricional da carne bovina e na saúde humana. O perfil dos seus ácidos graxos pode se apresentar de maneira diversificada conforme a genética, o manejo e a nutrição dos animais de origem. A deposição e composição da gordura são determinadas por muitos genes que participam direta ou indiretamente da adipogênese e do metabolismo lipídico. A seleção de animais com teor e composição de gordura adequado para o consumidor é complexa pela difícil mensuração destas características, pela moderada herdabilidade e pelo desconhecimento dos genes envolvidos. Na última década, presenciamos um grande avanço na área da genômica bovina que resultou no sequenciamento completo do genoma e no desenvolvimento de chips de alta densidade de SNP. Este progresso científico, aliado aos avanços tecnológicos de equipamentos, resultou na identificação de genes responsáveis pela determinação de características quantitativas de interesse científico e comercial na bovinocultura. Este estudo teve como objetivo identificar e caracterizar genes associados à deposição e composição de gordura intramuscular em bovinos Nelore. Para este fim foi conduzido um estudo de associação genômica (Genome-wide association studies, GWAS) para identificar regiões genômicas associadas às características de interesse e identificar genes candidatos posicionais. Para o estudo de expressão diferencial foi conduzido um estudo do transcriptoma a partir do sequenciamento de RNA total (RNA-Seq) do músculo Longissimus dorsi. Foram utilizados 386 Nelores para a avaliação do teor de lipídeos total e perfil de ácidos graxos do músculo LD e, genotipagem com chip de alta densidade de SNP (Illumina SNP800 BeadChip). Um subconjunto de 14 animais, sendo sete animais de cada extremo para os valores genômicos estimados (GEBV) foi utilizado para o estudo de RNA-Seq. Foram encontradas 25 regiões genômicas (intervalos de 1 MB) associadas com deposição e composição de gordura intramuscular, as quais explicaram >= 1% da variância genética. Estas regiões foram identificadas nos cromossomos 2, 3, 6, 7, 8, 9, 10, 11, 12, 17, 26 e 27, muitas destas não foram previamente detectadas em outras raças. Nestas regiões foram identificados importantes genes e podem ajudar no entendimento da base genética envolvida na deposição e composição de gordura. As regiões genômicas e genes aqui identificados e apresentados contribuem para um melhor entendimento do controle genético da deposição e composição de gordura em gado de corte e ainda podem ser aplicados em programas de seleção genética de animais que produzam carne com qualidade e com perfil de gordura saudável ao homem.

Background Obesity is increasing worldwide and is a major contributor to morbidity and mortality. Notably, abdominal (central) obesity carries a high risk of obesity-related diseases, while peripheral fat accumulation can act in a protective manner. A redistribution of fat from peripheral to central depots is seen after the menopause and is associated with an increasing prevalence of diabetes and cardiovascular disease. A key mediator may be ectopic fat accumulation in the liver. Our hypothesis was that a Palaeolithic-type diet (PD) consumed ad libitum improves body composition and metabolic risk markers, including liver fat and insulin sensitivity, in obese postmenopausal women. Methods In study I the study subjects (n=10) used a PD during 5 weeks. In study II and III (n=70) the effect of a Palaeolithic-type diet (PD) was compared to a diet according to the Nordic Nutrition Recommendations diet (NNR) during a 2-year randomized clinical trial (RCT). Food records and nitrogen excretion in urine validated food intake. Anthropometric measurements were performed in a standardized manner. Body composition was calculated using Dual Energy X-ray Absorptiometry (DXA). Total energy expenditure was calculated by accelerometry (Actiheart®) in combination with indirect calorimetry. Liver and muscle fat content was estimated by magnet resonance spectroscopy (1H-MRS). Insulin sensitivity was measured either with hyperinsulinemic euglycemic clamps (paper I) or oral glucose tolerance tests (OGTTs) (paper III). Results In study I a significant weight loss, linked to improved lipid and blood pressure levels, was associated with a 49% decrease in liver fat. Concomitantly, hepatic insulin sensitivity improved, while peripheral insulin sensitivity (and muscle fat) was unaltered. In study II/III both groups had a significant and sustained weight loss after 2 years. The PD was more effective than the NNR diet regarding loss of weight and fat mass after 6 months, but not after 24 months. Serum triglyceride levels were significantly lower at 24 months in the PD group. Liver fat decreased throughout the study in both groups. Hepatic insulin sensitivity improved during the first 6 months of the study, while peripheral insulin sensitivity did not change. Hepatic insulin sensitivity was associated with liver fat at baseline, but not during the diet intervention. Energy expenditure did not change in any of the study groups. Conclusion Ad libitum diets can have sustained beneficial effects on weight and body composition in obese postmenopausal women, a PD being more effective on short-term than a diet according to the NNR. This is associated with a reduction in liver fat that may reduce the risk of future diabetes and cardiovascular disease. Further studies are needed in order to explore the association between liver fat and metabolic dysfunction, including insulin sensitivity.

OBJECTIVE: The purpose of this study was to examine the relationship between strength training and body composition before and after controlling for several covariates. A cross-sectional study including 257 female subjects was conducted. METHODS: Subjects' level of involvement in strength training was determined via questionnaire. Body composition was assessed using dual energy X-ray absorptiometry (DXA). Diet was assessed using 7-d weighed food records. RESULTS: Strong linear relationships between subjects' level of involvement in strength training and body composition were identified. For each additional day of strength training reported per week, body fat was 1.32 percentage points lower (F = 14.8, p = 0.0002) and fat-free mass was 656.4 g (1.45 lb) higher (F = 18.9, p < 0.0001), on average. Likewise, the more time subjects spent lifting and the more intensely they trained, the better their body composition tended to be. Adjusting for differences in age, menopause status, objectively measured physical activity, energy intake, and protein intake tended to weaken each association. Controlling for differences in physical activity weakened each relationship the most. CONCLUSION: Women who strength train regularly tend to have significantly lower body fat percentages and significantly higher levels of fat-free mass compared to their counterparts, regardless of differences in several potential confounding variables.

Obesity is a major public health problem in both developed and developing countries. The body mass index (BMI) is the most common index used to define obesity. The universal application of the same BMI classification across different ethnic groups is being challenged due to the inability of the index to differentiate fat mass (FM) and fat�]free mass (FFM) and the recognized ethnic differences in body composition. A better understanding of the body composition of Asian children from different backgrounds would help to better understand the obesity�]related health risks of people in this region. Moreover, the limitations of the BMI underscore the necessity to use where possible, more accurate measures of body fat assessment in research and clinical settings in addition to BMI, particularly in relation to the monitoring of prevention and treatment efforts. The aim of the first study was to determine the ethnic difference in the relationship between BMI and percent body fat (%BF) in pre�]pubertal Asian children from China, Lebanon, Malaysia, the Philippines, and Thailand. A total of 1039 children aged 8�]10 y were recruited using a non�]random purposive sampling approach aiming to encompass a wide BMI range from the five countries. Percent body fat (%BF) was determined using the deuterium dilution technique to quantify total body water (TBW) and subsequently derive proportions of FM and FFM. The study highlighted the sex and ethnic differences between BMI and %BF in Asian children from different countries. Girls had approximately 4.0% higher %BF compared with boys at a given BMI. Filipino boys tended to have a lower %BF than their Chinese, Lebanese, Malay and Thai counterparts at the same age and BMI level (corrected mean %BF was 25.7�}0.8%, 27.4�}0.4%, 27.1�}0.6%, 27.7�}0.5%, 28.1�}0.5% for Filipino, Chinese, Lebanese, Malay and Thai boys, respectively), although they differed significantly from Thai and Malay boys. Thai girls had approximately 2.0% higher %BF values than Chinese, Lebanese, Filipino and Malay counterparts (however no significant difference was seen among the four ethnic groups) at a given BMI (corrected mean %BF was 31.1�}0.5%, 28.6�}0.4%, 29.2�}0.6%, 29.5�}0.6%, 29.5�}0.5% for Thai, Chinese, Lebanese, Malay and Filipino girls, respectively). However, the ethnic difference in BMI�]%BF relationship varied by BMI. Compared with Caucasians, Asian children had a BMI 3�]6 units lower for a given %BF. More than one third of obese Asian children in the study were not identified using the WHO classification and more than half were not identified using the International Obesity Task Force (IOTF) classification. However, use of the Chinese classification increased the sensitivity by 19.7%, 18.1%, 2.3%, 2.3%, and 11.3% for Chinese, Lebanese, Malay, Filipino and Thai girls, respectively. A further aim of the first study was to determine the ethnic difference in body fat distribution in pre�]pubertal Asian children from China, Lebanon, Malaysia, and Thailand. The skin fold thicknesses, height, weight, waist circumference (WC) and total adiposity (as determined by deuterium dilution technique) of 922 children from the four countries was assessed. Chinese boys and girls had a similar trunk�]to�]extremity skin fold thickness ratio to Thai counterparts and both groups had higher ratios than the Malays and Lebanese at a given total FM. At a given BMI, both Chinese and Thai boys and girls had a higher WC than Malays and Lebanese (corrected mean WC was 68.1�}0.2 cm, 67.8�}0.3 cm, 65.8�}0.4 cm, 64.1�}0.3 cm for Chinese, Thai, Lebanese and Malay boys, respectively; 64.2�}0.2 cm, 65.0�}0.3 cm, 62.9�}0.4 cm, 60.6�}0.3 cm for Chinese, Thai, Lebanese and Malay girls, respectively). Chinese boys and girls had lower trunk fat adjusted subscapular/suprailiac skinfold ratio compared with Lebanese and Malay counterparts. The second study aimed to develop and cross�]validate bioelectrical impedance analysis (BIA) prediction equations of TBW and FFM for Asian pre�]pubertal children from China, Lebanon, Malaysia, the Philippines, and Thailand. Data on height, weight, age, gender, resistance and reactance measured by BIA were collected from 948 Asian children (492 boys and 456 girls) aged 8�]10 y from the five countries. The deuterium dilution technique was used as the criterion method for the estimation of TBW and FFM. The BIA equations were developed from the validation group (630 children randomly selected from the total sample) using stepwise multiple regression analysis and cross�]validated in a separate group (318 children) using the Bland�]Altman approach. Age, gender and ethnicity influenced the relationship between the resistance index (RI = height2/resistance), TBW and FFM. The BIA prediction equation for the estimation of TBW was: TBW (kg) = 0.231�~Height2 (cm)/resistance (ƒ¶) + 0.066�~Height (cm) + 0.188�~Weight (kg) + 0.128�~Age (yr) + 0.500�~Sex (male=1, female=0) . 0.316�~Ethnicity (Thai ethnicity=1, others=0) �] 4.574, and for the estimation of FFM: FFM (kg) = 0.299�~Height2 (cm)/resistance (ƒ¶) + 0.086�~Height (cm) + 0.245�~Weight (kg) + 0.260�~Age (yr) + 0.901�~Sex (male=1, female=0) �] 0.415�~Ethnicity (Thai ethnicity=1, others=0) �] 6.952. The R2 was 88.0% (root mean square error, RSME = 1.3 kg), 88.3% (RSME = 1.7 kg) for TBW and FFM equation, respectively. No significant difference between measured and predicted TBW and between measured and predicted FFM for the whole cross�]validation sample was found (bias = �]0.1�}1.4 kg, pure error = 1.4�}2.0 kg for TBW and bias = �]0.2�}1.9 kg, pure error = 1.8�}2.6 kg for FFM). However, the prediction equation for estimation of TBW/FFM tended to overestimate TBW/FFM at lower levels while underestimate at higher levels of TBW/FFM. Accuracy of the general equation for TBW and FFM compared favorably with both BMI�]specific and ethnic�]specific equations. There were significant differences between predicted TBW and FFM from external BIA equations derived from Caucasian populations and measured values in Asian children. There were three specific aims of the third study. The first was to explore the relationship between obesity and metabolic syndrome and abnormalities in Chinese children. A total of 608 boys and 800 girls aged 6�]12 y were recruited from four cities in China. Three definitions of pediatric metabolic syndrome and abnormalities were used, including the International Diabetes Federation (IDF) and National Cholesterol Education Program (NCEP) definition for adults modified by Cook et al. and de Ferranti et al. The prevalence of metabolic syndrome varied with different definitions, was highest using the de Ferranti definition (5.4%, 24.6% and 42.0%, respectively for normal�]weight, overweight and obese children), followed by the Cook definition (1.5%, 8.1%, and 25.1%, respectively), and the IDF definition (0.5%, 1.8% and 8.3%, respectively). Overweight and obese children had a higher risk of developing the metabolic syndrome compared to normal�]weight children (odds ratio varied with different definitions from 3.958 to 6.866 for overweight children, and 12.640�]26.007 for obese children). Overweight and obesity also increased the risk of developing metabolic abnormalities. Central obesity and high triglycerides (TG) were the most common while hyperglycemia was the least frequent in Chinese children regardless of different definitions. The second purpose was to determine the best obesity index for the prediction of cardiovascular (CV) risk factor clustering across a 2�]y follow�]up among BMI, %BF, WC and waist�]to�]height ratio (WHtR) in Chinese children. Height, weight, WC, %BF as determined by BIA, blood pressure, TG, high�]density lipoprotein cholesterol (HDL�]C), and fasting glucose were collected at baseline and 2 years later in 292 boys and 277 girls aged 8�]10 y. The results showed the percentage of children who remained overweight/obese defined on the basis of BMI, WC, WHtR and %BF was 89.7%, 93.5%, 84.5%, and 80.4%, respectively after 2 years. Obesity indices at baseline significantly correlated with TG, HDL�]C, and blood pressure at both baseline and 2 years later with a similar strength of correlations. BMI at baseline explained the greatest variance of later blood pressure. WC at baseline explained the greatest variance of later HDL�]C and glucose, while WHtR at baseline was the main predictor of later TG. Receiver�]operating characteristic (ROC) analysis explored the ability of the four indices to identify the later presence of CV risk. The overweight/obese children defined on the basis of BMI, WC, WHtR or %BF were more likely to develop CV risk 2 years later with relative risk (RR) scores of 3.670, 3.762, 2.767, and 2.804, respectively. The final purpose of the third study was to develop age�] and gender�]specific percentiles of WC and WHtR and cut�]off points of WC and WHtR for the prediction of CV risk in Chinese children. Smoothed percentile curves of WC and WHtR were produced in 2830 boys and 2699 girls aged 6�]12 y randomly selected from southern and northern China using the LMS method. The optimal age�] and gender�]specific thresholds of WC and WHtR for the prediction of cardiovascular risk factors clustering were derived in a sub�]sample (n=1845) by ROC analysis. Age�] and gender�]specific WC and WHtR percentiles were constructed. The WC thresholds were at the 90th and 84th percentiles for Chinese boys and girls, respectively, with sensitivity and specificity ranging from 67.2% to 83.3%. The WHtR thresholds were at the 91st and 94th percentiles for Chinese boys and girls, respectively, with sensitivity and specificity ranging from 78.6% to 88.9%. The cut�]offs of both WC and WHtR were age�] and gender�]dependent. In conclusion, the current thesis quantifies the ethnic differences in the BMI�]%BF relationship and body fat distribution between Asian children from different origins and confirms the necessity to consider ethnic differences in body composition when developing BMI and other obesity index criteria for obesity in Asian children. Moreover, ethnicity is also important in BIA prediction equations. In addition, WC and WHtR percentiles and thresholds for the prediction of CV risk in Chinese children differ from other populations. Although there was no advantage of WC or WHtR over BMI or %BF in the prediction of CV risk, obese children had a higher risk of developing the metabolic syndrome and abnormalities than normal�]weight children regardless of the obesity index used.

Background: Overweight and obesity constitutes a threat to public health all around the world, and more individual’s dies from obesity than from hunger. This condition is increasing worldwide and obesity also occurs in children. According to WHO, there are 42 million overweight children in the world. Obesity and overweight in childhood leads to insulin resistance, elevated blood lipids and cardiovascular effects. Obesity is caused by positive energy intake, poor exercise habits, environmental factors, food habits and stress etc. It is also known that hormones influence the incidence of obesity. It has been found that individuals with overweight and obesity has elevated glucagon levels in the bloodstream Purpose: This work aims to investigate whether there is a difference in glucagon concentration between the sexes at ages 10-18 years with obesity, and if there is an association between glucagon concentration and weight, FM and FFM. Materials and Methods: In this study, obesity is determined by BIA and the caliper in combination as three compartment model. Blood samples were taken by venipuncture and glucagon were analyzed in fasting plasma. Results: BIA and the caliper together had a significant correlation with body composition. Blood glucagon was found to be high in obese children. Conclusion: Glucagon concentration in obese children correlates with weight and FM. However, further investigation is needed regard to how glucagon interact with weight, FM and FFM

The financial value of a carcass is influenced by lean meat yield percentage (LMY%), which represents the proportion of the carcass that is lean meat (muscle). Australian lamb producers can select for this trait indirectly via three existing Australian Sheep Breeding Values (ASBVs), namely post-weaning weight (PWWT), c-site fat depth (PFAT) and eye muscle depth (PEMD). Previous research assessing the effect of these breeding values on carcass composition has focussed on individual point measurements of tissue depth or the weights of a small number of indicator muscles. In contrast, this PhD has used computed tomography (CT) scanning to assess the impact of ASBVs on composition at a whole carcass level. Chapters 3 and 4 of this thesis focus on the change in body composition (fat, lean and bone), in the fore, saddle (middle) and hind sections of the carcass as measured by CT. An allometric approach was adopted in the analysis of the data from 1,665 lamb carcasses, which allowed a robust interpretation of the impact of the carcass breeding values and production factors on carcass composition. It was discovered that increasing sire PEMD and reducing sire PFAT increased LMY% (7.7% and 9.5% units) across the range of these breeding values. Furthermore, lean was redistributed to the saddle region (3.8% units for PEMD and 3.7% units for PFAT). Additionally both breeding values reduced carcass fatness across the sire range by 24.7% and 16.6% for PFAT and PEMD respectively. Increasing sire PWWT had minimal impact on LMY% and carcass fat. Carcass bone was most influenced by reducing sire PFAT, with the other breeding values having little (PWWT) or no (PEMD) effect. Chapter 5 uses further analysis of data collected in Chapters 3 and 4 to report on the financial implications of using ASBVs to select for improved LMY%. The use of CT to report the financial improvement to carcass lean value achieved through genetic selection has not previously been comprehensively reported. Lambs were compared at a standard carcass weight (23kg) and age (269 days), which allowed the influence of the breeding values on both LMY% and HCWT to be accounted for in the calculation of carcass lean value. Reducing sire PFAT had the greatest impact on carcass lean value followed by PEMD and PWWT. The eating quality and nutritive value of lamb are essential traits for consumer satisfaction. Selection for leanness has been shown to reduce intramuscular fat (IMF) in the loin (longissimus lumborum) muscle and so have a detrimental impact on eating quality. For this reason, selection to improve LMY% must be balanced against the consumer focused traits. The measurement of IMF% in relation to genetic selection is undertaken in the loin muscle, with little known about the other muscles of the carcass. Chapters 6 and 7 detail the correlation of IMF% between 5 muscles located in different carcass regions (fore, saddle and hind). These correlations were generally found to be strong, particularly for that of the loin IMF% with the fore and hind section muscles. From an industry perspective this is a significant outcome, as it implies that genetic selection for IMF% in the loin will also cause correlated changes in the other muscles. The relationship between LMY% and IMF% in each of these muscles was also assessed, and found to be consistently negative. Lastly, CT was assessed for its effectiveness to predict IMF%. Although a negative correlation was found between average pixel density and IMF%, the ability of CT scanning to predict IMF% demonstrated relatively poor precision. In summary this work has utilised CT to quantify the impact of ASBVs on carcass composition in lamb. It details the financial impact of these effects due to changes in lean % and its distribution throughout the carcass. Additionally it explores the relationship between IMF% in different regions of the carcass and the impact of selection for LMY%. Finally it assesses the ability of CT to predict IMF% which would be of benefit to industry in the event that CT measurement becomes mainstream within commercial abattoirs.

Background: In recent years several state high school athletic association have investigated methods to ensure the health and safety of high school wrestlers. One method implemented by the National Collegiate Athletic Association requires the prediction of minimum weight (MW) prior to the competition season. This weight certification program requires the assessment of body composition and hydration status. Results from those assessments place wrestlers in their lowest allowable wrestling weight class. There are a variety of measurement devises that have proven to be effective in measuring body composition. However, several considerations must be taken into account when choosing a devise such as affordability and reliability. Of those devices leg-to-leg bioelectrical impedance analysis (BIA) has been suggested for use with wrestlers. Purpose: To test the validity of bioelectrical impedance as an instrument of body composition and minimum wrestling weight compared to three-site skinfold using the Lohman-Brozek formula and the Bod Pod®; among hydrated high school wrestlers. Methods: Criterion for this study was the Bod Pod®. Subjects included 98 high school wrestlers taking part in the pre-season wrestling weight certification program implemented by the Virginia High School League. Hydration was assessed and a urine specific gravity (USG) ≤ 1.020 was assigned as the level of hydration. Results: In order to investigate the validity of BIA in this study a repeated measure ANOVA with between-subjects factors was used to assess the equality of means between the three measurement devices. Also, in order to investigate hydration affect subjects were divided into two categories (hydrated and dehydrated). Finally, prior to analysis subjects were placed in weight categories based on their assigned wrestling weight class. Results of this study demonstrated that the three measurement devices did not produce similar results and it was concluded that hydration level had no affect on the measurements. Therefore, at this time BIA should not be considered as an alternative method for assessing body composition in high school wrestling weight certification programs.
Ph. D.

The purpose of this study was to investigate differences among the percent body fat (%BF) values of Turkish sedentary male and female university students measured by dual-energy x-ray absorptiometry (DEXA), skinfold (SKF), ultrasound (US) and hand to hand bioelectrical impedance analysis (BIA). Two hundred eight Turkish university students (one hundred four males and one hundred four females) aged between 18 to 26 years old participants participated in this study voluntarily. %BF assessment was performed by the SKF, US, BIA and DEXA methods. Differences among DEXA, SKF, US and BIA were examined by applying a series of paired-t test. Multiple regression analyses were conducted to developed regression equations to predict %BF from SKF and US measurements. Results demonstrated that there were significant differences between DEXA and SKF, US, and BIA measurements for males and females. The mean %BF derived from DEXA was significantly (p<
.001) greater than those of SKF, US and BIA for males and females. Multiple regression analyses showed that SKF and US measurement of subcutaneous fat at three-sites gave the best prediction to %BF for male and female separately. The multiple correlations using three sites simultaneously for men and women were r=0.92, SEE=2.4 and r=0.91, SEE=2.8 for SKF and r=0.93, SEE=2.3 and r=0.90, SEE=3.0 for US, respectively. In summary, with the new regression equation US appears to be a reliable, portable, and non-invasive tool which can be used by any field investigator on obese or thin individuals. Finally, new regression equations developed do not seem to be superior to those reported using calipers.

This study examined percent fat, fat distribution, and resting cortisol concentrations between personality types for coronary artery disease (CAD) risk. Males (n= 29, 43 ± 8.8 years) selected through the Jenkins Activity Survey, scoring >_ 75th percentile (Type A=15) or S 30th percentile (Type B=14), had the following measures: percent fat, lipid profile, and waist-to-hip ratio. Each hour, heart rate, blood pressure (SBP, DBP), and cortisol were measured. A prediction model determined risk of CAD. Type A had a tendency to have higher DBP, but was only significant at one time point (F= 3.390, p= .022). Type B showed significantly higher total (t= -2.688, p= .012) and LDL cholesterol (t= -3.612, p= .001). Although we did not show many significant differences between groups, within groups, many significant correlations were detected among the variables measured. Further studies will justify the associations between percent fat, fat distribution, and cortisol across personality types.
School of Physical Education

Background: The metabolic syndrome affects 10-35% of the European population and increases type 2 diabetes mellitus and cardiovascular disease. risk by 2.8-8 and 1.5-6 fold, respectively. Prospective evidence suggests dietary fat composition may modify components of the syndrome, including insulin resistance and endothelial dysfunction. Aim: To investigate the impact of dietary fat composition on insulin sensitivity (Si) and endothelial dysfunction. Methods: The effects of dietary fat quality and quantity were investigated.in a large (n =417), pan-European, dietary intervention trial p2 weeks), carried out in free-living participants with the metabolic syndrome. Multiple regression analysis identified key determinants of Si and endothelial dysfunction in this population and in a group of healthy, aged-matched subjects (n =239). A comparative investigation of the effects of a range of fatty acids on endothelial inflammatory gene expression was also performed using real time RT-PCR. Results: An increase in percentage energy from (%E) saturated fatty acids (SFA) decreased Si (t =0.055). Increased %E monounsaturated fatty acids (MUFA) reduced fasting insulin levels (p =0.03). The in vivo and in vitro investigations showed fat quality differentially affected endothelial function. In multiple regression analysis, key independent determinants of endothelial dysfunction and insuli~ resistance were insulin sensitivity (2.9-6.4%) and endothelial function (1.9-5.3%), respectively. Waist, gender, triacylglycerol and non-esterified fatty acid levels were also important determinants of Si. Results showed gender specific effects on the responsiveness of some metabolic factors to dietary intervention and also suggested disease state may be important. Conclusion: Substitution of SFA for MUFA may represent a strategy to improve insulin sensitivity in those with the metabo'lic syndrome. However, the practical attainment of an adequate level of substitution may be a limiting factor. Further work is required to elucidate the role of insulin action in the effects of fatty acids on endothelial function.

Purpose: The purpose of this study was to assess the relationship between intensity of physical activity and body composition in 239 young adult women. Methods: This study was cross-sectional. Participants were recruited from October 2009 to December 2011 and included women from 36 different states and 6 different countries. Physical activity was objectively measured using accelerometers worn for seven days. Body composition was measured using the BOD POD. Height, weight, and circumferences were assessed. Results: Participant's mean age was 20.6±1.6 years. Their mean BMI was 22.6±3.0 kg/m2 and mean body fat percentage was 26.4±6.3 %. Average total activity counts per day were 387,560 ± 172,000, with 61.6±22.5 min per day spent in MVPA, 169.4±43 min per day in light activity, 55.6±19 min per day in moderate activity, and 6±9.2 min per day in vigorous activity. Total activity counts per day were inversely correlated with body fat (r = -0.17, p = 0.007). Light activity was positively correlated with both BMI (r = 0.17, p = 0.007) and waist circumference (r = 0.15, p = 0.0164). Moderate activity was inversely associated with body fat (r = -0.18, p = 0.0051) and hip circumference (r = -0.12, p = 0.0459). MVPA was inversely associated with body fat (r = -0.19, p = 0.0026) and hip circumference (r = -0.14, p = 0.0291). Vigorous physical activity was inversely related to body fat (r = -0.20, p = 0.0023). Using stepwise regression, the best predictor of body fat was time spent in vigorous PA (F = 9.45, p = 0.0024). The best predictor of BMI was light activity per day, which was positively correlated with BMI (F = 7.5, p = 0.0066) followed by moderate activity per day which was negatively correlated (F = 4.25, p = 0.0403). Young adult women who spent no time performing vigorous PA had significantly higher body fat percentages than women who performed some vigorous PA. Young adult women who spent less than 30 minutes per day in MVPA had significantly higher body fat percentages and BMIs than those who obtained more than 30 minutes per day. For every 10 minutes spent in MVPA per day, the odds of being obese by body fat decreased by 33%. Conclusion: Vigorous PA and MVPA appear to be the most important aspects of PA associated with lower body fat and BMI levels. Young adult women should be encouraged to obtain at least 30 minutes of MVPA per day.

The purpose of this study was to determine the effect of 100% cotton underwear worn beneath a swimsuit on the accuracy and reliability of percent body fat measurements in the BOD POD. Sixty adults (30 males, 30 females) of various ages (1887 years) and body composition (1.95-57.15%) were tested four times in one day. Subjects wore a swimsuit and swimcap for two trials and 100% cotton underwear beneath the swimsuit and a swimcap for the remaining trials. The clothing order was randomized. Thoracic gas volume was predicted. ANOVA found no significant difference between the swimsuit only trials (25.4+12.4%) and swimsuit with underwear trials (25.1+12.3%) for all subjects. Intra-class correlation coefficients were 0.994 and 0.995 for the swimsuit only and swimsuit with underwear trials, respectively. In conclusion, these results suggest that wearing 100% cotton underwear beneath a swimsuit is an acceptable practice for fitness laboratories and the reliability was very good.
School of Physical Education

Rates of obesity (OB) are escalating among Canadian children and youth and the obesogenic environment is likely to cause further increases. An important aspect in providing clinical care to OB children is to have accurate assessment measures, particularly of their body composition and cardiorespiratory fitness. This project entails three interrelated projects aiming to develop novel cardiorespiratory fitness and body composition measurement techniques for an OB pediatric population. The purpose of the first project was to validate a new submaximal fitness protocol specifically geared towards OB children and youth. The second objective of this thesis involved assessing cardiorespiratory efficiency utilizing the Oxygen Uptake efficiency slope. The purpose of the third project was to determine the validity of a half-body scan methodology for measuring body composition in obese children and youth. The goal of developing these novel measurement techniques is improved design and evaluation of interventions aimed at managing pediatric obesity.

Human immunodeficiency virus (HIV) that leads to acquired immune deficiency syndrome (AIDs) reduces immune function, resulting in opportunistic infections and later death. Use of antiretroviral therapy (ART) increases chances of survival, however, with some concerns regarding fat re-distribution (lipodystrophy) which may encompass subcutaneous fat loss (lipoatrophy) and/or fat accumulation (lipohypertrophy), in the same individual. This problem has been linked to Antiretroviral drugs (ARVs), majorly, in the class of protease inhibitors (PIs), in addition to older age and being female. An additional concern is that the problem exists together with the metabolic syndrome, even when nutritional status/ body composition, and lipodystrophy/metabolic syndrome are unclear in Uganda where the use of ARVs is on the increase. In line with the literature, the overall aim of the study was to assess physical characteristics of HIV-infected patients using a comprehensive anthropometric protocol and to predict body composition based on these measurements and other standardised techniques. The other aim was to establish the existence of lipodystrophy, the metabolic syndrome, andassociated risk factors. Thus, three studies were conducted on 211 (88 ART-naïve) HIV-infected, 15-49 year-old women, using a cross-sectional approach, together with a qualitative study of secondary information on patient HIV and medication status. In addition, face-to-face interviews were used to extract information concerning morphological experiences and life style. The study revealed that participants were on average 34.1±7.65 years old, had lived 4.63±4.78 years with HIV infection and had spent 2.8±1.9 years receiving ARVs. Only 8.1% of participants were receiving PIs and 26% of those receiving ART had ever changed drug regimen, 15.5% of whom changed drugs due to lipodystrophy. Study 1 hypothesised that the mean nutritional status and predicted percent body fat values of study participants was within acceptable ranges; different for participants receiving ARVs and the HIV-infected ART-naïve participants and that percent body fat estimated by anthropometric measures (BMI and skinfold thickness) and the BIA technique was not different from that predicted by the deuterium oxide dilution technique. Using the Body Mass Index (BMI), 7.1% of patients were underweight (<18.5 kg/m2) and 46.4% were overweight/obese (≥25.0 kg/m2). Based on waist circumference (WC), approximately 40% of the cohort was characterized as centrally obese. Moreover, the deuterium dilution technique showed that there was no between-group difference in the total body water (TBW), fat mass (FM) and fat-free mass (FFM). However, the technique was the only approach to predict a between-group difference in percent body fat (p = .045), but, with a very small effect (0.021). Older age (β = 0.430, se = 0.089, p = .000), time spent receiving ARVs (β = 0.972, se = 0.089, p = .006), time with the infection (β = 0.551, se = 0.089, p = .000) and receiving ARVs (β = 2.940, se = 1.441, p = .043) were independently associated with percent body fat. Older age was the greatest single predictor of body fat. Furthermore, BMI gave better information than weight alone could; in that, mean percentage body fat per unit BMI (N = 192) was significantly higher in patients receiving treatment (1.11±0.31) vs. the exposed group (0.99±0.38, p = .025). For the assessment of obesity, percent fat measures did not greatly alter the accuracy of BMI as a measure for classifying individuals into the broad categories of underweight, normal and overweight. Briefly, Study 1 revealed that there were more overweight/obese participants than in the general Ugandan population, the problem was associated with ART status and that BMI broader classification categories were maintained when compared with the gold standard technique. Study 2 hypothesized that the presence of lipodystrophy in participants receiving ARVs was not different from that of HIV-infected ART-naïve participants. Results showed that 112 (53.1%) patients had experienced at least one morphological alteration including lipohypertrophy (7.6%), lipoatrophy (10.9%), and mixed alterations (34.6%). The majority of these subjects (90%) were receiving ARVs; in fact, all patients receiving PIs reported lipodystrophy. Period spent receiving ARVs (t209 = 6.739, p = .000), being on ART (χ2 = 94.482, p = .000), receiving PIs (Fisher’s exact χ2 = 113.591, p = .000), recent T4 count (CD4 counts) (t207 = 3.694, p = .000), time with HIV (t125 = 1.915, p = .045), as well as older age (t209 = 2.013, p = .045) were independently associated with lipodystrophy. Receiving ARVs was the greatest predictor of lipodystrophy (p = .000). In other analysis, aside from skinfolds at the subscapular (p = .004), there were no differences with the rest of the skinfold sites and the circumferences between participants with lipodystrophy and those without the problem. Similarly, there was no difference in Waist: Hip ratio (WHR) (p = .186) and Waist: Height ratio (WHtR) (p = .257) among participants with lipodystrophy and those without the problem. Further examination showed that none of the 4.1% patients receiving stavudine (d4T) did experience lipoatrophy. However, 17.9% of patients receiving EFV, a non-nucleoside reverse transcriptase inhibitor (NNRTI) had lipoatrophy. Study 2 findings showed that presence of lipodystrophy in participants receiving ARVs was in fact far higher than that of HIV-infected ART-naïve participants. A final hypothesis was that the prevalence of the metabolic syndrome in participants receiving ARVs was not different from that of HIV-infected ART-naïve participants. Moreover, data showed that many patients (69.2%) lived with at least one feature of the metabolic syndrome based on International Diabetic Federation (IDF, 2006) definition. However, there was no single anthropometric predictor of components of the syndrome, thus, the best anthropometric predictor varied as the component varied. The metabolic syndrome was diagnosed in 15.2% of the subjects, lower than commonly reported in this population, and was similar between the medicated and the exposed groups (χ 21 = 0.018, p = .893). Moreover, the syndrome was associated with older age (p = .031) and percent body fat (p = .012). In addition, participants with the syndrome were heavier according to BMI (p = .000), larger at the waist (p = .000) and abdomen (p = .000), and were at central obesity risk even when hip circumference (p = .000) and height (p = .000) were accounted for. In spite of those associations, results showed that the period with disease (p = .13), CD4 counts (p = .836), receiving ART (p = .442) or PIs (p = .678) were not associated with the metabolic syndrome. While the prevalence of the syndrome was highest amongst the older, larger and fatter participants, WC was the best predictor of the metabolic syndrome (p = .001). Another novel finding was that participants with the metabolic syndrome had greater arm muscle circumference (AMC) (p = .000) and arm muscle area (AMA) (p = .000), but the former was most influential. Accordingly, the easiest and cheapest indicator to assess risk in this study sample was WC should routine laboratory services not be feasible. In addition, the final study illustrated that the prevalence of the metabolic syndrome in participants receiving ARVs was not different from that of HIV-infected ART-naïve participants.

The body composition of female collegiate athletes was measured using the Bod Pod® device. The sample consisted of 75 student athletes, aged 18 to 22 years old. Five sports at the university level were represented, including basketball, gymnastics, soccer, swimming & diving, and soccer. Participants were measured at the preseason and postseason periods. Overall, participants in all five sports were not found to change significantly in total body mass, fat mass, fat free mass, percent body fat, or body mass index from the preseason period to the postseason period at the alpha = 0.05 level. On average, the members from each of the different teams were found to be significantly different from each other for one or more variables. In general, basketball and volleyball players were found to be similar in body composition. The average member on the swimming & diving, soccer, and gymnastics teams was found to vary from the average team member on each of the other teams.

Elevated risk of cardiometabolic disease is magnified by variation in body fat distribution, in particular increased accumulation of visceral fat. Genome-wide association studies have mainly focused on anthropometric indices such as WHR and BMI to assess adiposity. They successfully identified over 100 loci highlighting for total fat mainly pathways in the brain involved in the regulation of energy expenditure and appetite and for fat distribution genes expressed in adipose and the periphery. Although genetic variants affecting localised fat deposition are known, the functional mechanisms of regional fat accumulation remain poorly understood. Here, we aimed to explore the genetic contribution to body composition to gain further mechanistic insight, and increase our understanding of the role of such genetic variants in metabolic health. We focused on the isolated population of Orkney. 1,301 participants from the Orkney Complex Disease Study, ORCADES underwent DXA scans allowing direct assessment of fat mass in various depots around the body. Genetic data imputed to the 1000 Genomes Project enabled the investigation of 35 million genetic variants. We first used univariate and bivariate analysis to quantify the contribution of genetic factors to the variation of body composition and establish genetic correlations with metabolic traits. We carried out genome-wide association analyses for body composition to identify new underlying genetic loci. We sought to replicate these findings in the Icelandic AGES cohort and the UK Biobank, with 3,219 and 1,575 participants with body composition analysis, respectively. We investigated the coding variation or the regulatory landscape around the associated variants to understand their functional impact. We further focused on one of the associated loci in greater detail. To establish a potential, causal gene for the associated variants and understand the impact of genetic variation on the regulatory elements, we carried out chromatin conformation studies around ENPP6 by. We then explored the role of causal gene candidate on body composition and metabolic health in an animal mouse model. Individual fat depots were moderately heritable with heritability estimates ranging from 35-50% in ORCADES. The genetic correlations with metabolic traits were highest with android, and visceral fat and the ratio of android and gynoid fat percentage: Insulin (0.68-0.75), HOMA-B (0.58-0.70), HOMA-IR (0.69-0.75), CRP (0.47-0.55) and DBP (0.49-0.58). Genome-wide association analysis identified three regions associated with body composition: VRTN, EXOC6B and ENPP6. Low frequency variants on chromosome 4, mapping within the ENPP6 gene associated with the ratio of android and gynoid fat (p= 4.5x10-10), which replicated in abdominal fat by CT in AGES (p=0.003). Per allele, variant carriers show a reduction in android fat by 3% and visceral fat of 140g as well as lowered diastolic blood pressure of 10mmHg. Due to this evidence ENPP6 was chosen as a focus for further mechanistic and functional studies. The lead SNPs map to an ENCODE-predicted DNase1 hypersensitivity site within the second intron of the ENPP6 gene, suggesting a role in genome regulation. Marking the areas with sequence-specific probes by 3D fluorescent in situ hybridisation confirmed that the association interval co-localised more frequently with the ENPP6 promoter than with other gene promoters within the same chromosomal region in SH-SY5Y neurons (p=0.01) but not human SGBS adipocytes. This indicates ENPP6 as a possible causal gene. Consistent with this ENPP6 mRNA levels were extremely low in human subcutaneous and visceral adipose tissue. ENPP6 expression is highest in the brain and kidney, suggesting a neuronal/renal mediated mechanism driving body composition. To model the impact of Enpp6 on adiposity in vivo, Enpp6-/- mice were generated and their metabolic profile investigated. Enpp6-/- mice showed a decrease in visceral fat depot and improved glucose tolerance (n= 24, pfat=0.002, pGTT=0.001). However, no difference was found with regards to their feeding or physical activity behaviour, suggesting an intrinsic alternative to maintaining an energy balance. Using the advantage of genetic drift in a population isolate and direct fat phenotyping we confirmed the contribution of genetic variants to variation in body composition and describe the involvement of three particular loci VRTN, EXOC6B and ENPP6. In particular, we describe ENPP6 as a likely neuronal mechanism underlying selectively visceral adiposity in humans and mice. This study sets a starting point for the investigation into ENPP6 as an anti-obesity and anti-diabetes therapeutic.

Background: Rheumatoid arthritis (RA) is characterised by excessive production of tumour necrosis factor alpha (TNFα). This leads to rheumatoid cachexia, a condition characterised by increased resting energy expenditure (REE) and loss of fat-free mass (FFM) leading to functional disability, decreased strength and balance. The aims of this research work was to: a) to develop a new REE equation in order to continuously monitor abnormal changes in REE in the RA population, b) to investigate if smoking further enhances hypermetabolism and c) to examine if the new anti-TNFα medication reverses this metabolic abnormality. Methods: 68 patients with RA were assessed for demographic and anthropometrical characteristics, REE (indirect calorimetry), body composition (bioelectrical impedance), and disease activity [C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), disease activity score 28 (DAS28) and health assessment questionnaire (HAQ)]. 20 of the total 68 patients, about to start anti-TNFα therapy, underwent the exact same aforementioned procedures but on three separate occasions (Baseline: two weeks prior to anti-TNFα treatment, Time-1 and Time-2: two weeks and three months, respectively, after the drug had been introduced. Results: Study 1: Based on FFM and CRP, a new equation was developed which had a prediction power of R2=0.76. The new equation revealed an almost identical mean with measured REE (1645.2±315.2 and 1645.5±363.1 kcal/day, p>0.05), and a correlation coefficient of r=0.87 (p=0.001). Study 2: Smokers with RA demonstrated significantly higher REE (1513.9±263.3 vs. 1718.1±209.2 kcal/day; p=0.000) and worse HAQ (1.0±0.8 vs. 1.7±0.8; p=0.01) compared to age and FFM matched RA non-smokers. The REE difference was significantly predicted by the interaction smoking/gender (p=0.04). Study 3: Significant increases were observed in REE (p=0.002), physical activity (p=0.001) and protein intake (p=0.001) between the three times of assessment. Moreover, disease activity significantly reduced [ESR (p=0.002), DAS28 (p=0.000), HAQ (p=0.000) and TNFα (p=0.024)] while FFM and total body fat did not change (both at p>0.05). Physical activity and protein intake were found to be significant within-subject factors for the observed REE elevation after 12-weeks on anti-TNFα treatment (p=0.001 and p=0.024, respectively). Conclusions: Findings from the first study revealed that the newly developed REE equation provides an accurate prediction of REE in RA patients. Moreover, the results from the second study showed that cigarette smoking further increases REE in patients with RA and has a negative impact on patients’ self-reported functional status. Finally, our data from the third study suggest that REE remains elevated not because of the maintenance of the RA-related hypermetabolism but due to the concomitant significant increases in physical activity and protein intake.