Adolescência é o período de transição entre a infância e a vida adulta, caracterizado pelos impulsos do desenvolvimento físico, mental, emocional, sexual e social. Essa faixa etária, ao longo dos anos tem apresentado aumento da prevalência de sobrepeso e obesidade e danos e agravos à saúde provocados pelas comorbidades associadas. Os fatores que contribuem para esse processo são a alimentação e a inatividade física, portanto conhecer e saber escolher o melhor método para avaliar gasto energético basal e total, atividade física e a composição corporal dessa população ajuda os profissionais da saúde a trilharem soluções mais promissoras para o combate da obesidade e a formação de adultos mais saudáveis. O objetivo principal do presente estudo foi avaliar Gasto Energético e fatores diretamente relacionados como Consumo Alimentar e Padrão de Atividade Física em Adolescentes Obesos e Eutróficos. Foram estudados 86 adolescentes obesos e eutróficos de idade de 11 a 14 anos de ambos os sexos de escolas públicas e particulares de Ribeirão Preto. Foi avaliada a atividade física por meio do acelerômetro tri-axial, a composição corporal por absorcimetria de raio X de dupla energia, bioimpedância elétrica e óxido de deutério e gasto energético basal por calorimetria indireta e gasto energético total por água duplamente marcada. Os dados foram analisados pelo teste de normalidade Kolmogorov Smirnov, teste Anova com pós teste de Tukey e comparações por método Bland-Altman. O peso muscular pelo DXA de adolescentes obesos foi maior do que em adolescentes eutróficos. Houve diferença estatística entre obesos e eutróficos nas variáveis MMkg, MM%, MGkg e MG%. Analisando a composição corporal por BIA e OD podemos ver que a BIA superestima os resultados. Quanto ao gasto energético, não houve diferença estatística entre os grupo em relação ao GEB e GET, para o GET ser maior independe da atividade física em número de passos no dia, pois o GEB em X obesos (meninos e meninas) é maior quando comparado com eutróficos. O nível de atividade física dos adolescentes se mostrou semelhante entre os obesos e eutróficos, apesar dos obesos darem muito menos passos ao longo do dia. Em nosso estudo todas as variáveis foram diferentes entre os grupos. Foi constatado que os adolescentes obesos apresentam maior GEB por terem maior massa muscular, o que já eleva o GET, apesar de apresentarem AF menos intensa que os eutróficos, confirmando nossa hipótese inicial. / Adolescence is the transitional period between childhood and adulthood, characterized by the impulses of the physical, mental, emotional, sexual and social development. This age group, all over the years, has shown increasing prevalence of overweight and obesity, damage and health problems caused by associated comorbidities. Factors that contribute to this process are the diet and physical inactivity, so knowing how to choose the best method to assess basal and total energy expenditure, physical activity and body composition of this population helps health professionals to find the best solutions to deal with obesity and how to guide their patients on how to become healthier adults. The main objective of this study was to evaluate Energy Expenditure and directly related factors such as Food Consumption and Physical Activity in Adolescents Obese and Eutrophic. We studied 86 adolescents aged between 11 and 14 years of both genders, obese and non-obese, from public and private schools in Ribeirão Preto. Physical Activity was evaluate by tri-axial accelerometer, body composition by dual-energy X-ray absorptiometry, electric bioimpedance and deuterium oxide, and basal energy expenditure was evaluate by indirect calorimetry and total energy expenditure by doubly labeled water. Data was analysed by Kolmogorov Smirnov to check normality, Anova with post test Tukey and comparisons by Bland-Altman method. The muscle weight by DXA of obese adolescents was higher than in normal weight adolescents. There was statistical difference between obese and normal weight in MMkg variables, MM % BFkg and BF %. Analyzing body composition by BIA and OD we can see that the BIA overestimates the results. In relation to the energy expenditure, there was no statistical difference between the groups in relation to the REE and TEE to the TEE be most independent of physical activity in number of steps in the day, because the REE in obese (boys and girls) is higher as compared with eutrophic. XII The level of physical activity in adolescents was similar between the obese ones and normal weight ones, while obese ones had much less steps throughout the day. In our study all the variables were different between the grupos. We found that obese adolescents have higher REE because they have more muscle mass, which already raises the TEE, despite having less intense physical activity that eutrophic adolescents, confirming our initial hypothesis.

Introdução a redução da massa muscular esquelética relacionada à idade, denominada sarcopenia, está associada com maior incidência de quedas, fraturas e dependência funcional em idosos. Muitos são os fatores que podem contribuir para o surgimento da sarcopenia, dentre eles a deficiência de vitamina D e a inadequação do consumo alimentar, principalmente a ingestão de proteína. Objetivos investigar a relação da sarcopenia com o consumo alimentar e concentração sérica de 25(OH)D. Métodos Foram avaliadas 200 mulheres acima de 65 anos, sendo 35 com sarcopenia e 165 sem sarcopenia. Avaliou-se a densidade mineral óssea (DMO) da coluna lombar, fêmur proximal e a composição corporal (massa muscular total, massa muscular esquelética, massa adiposa, conteúdo mineral ósseo do corpo total) por meio do densitômetro de dupla emissão com fonte de raios-X (DXA), avaliação radiográfica das colunas dorsal e lombar (T4 a L4). Foi realizada também avaliação da ingestão alimentar (diário de três dias), bioquímica do metabolismo mineral e ósseo (cálcio total, fósforo, creatinina, albumina, paratormônio intacto, calcidiol) e a história clínica das pacientes. Resultados O presente estudo observou que as pacientes que apresentavam um consumo de proteína acima de 1,2g/kg/dia apresentaram massa muscular total [33,94 (4,72) vs 31,87 (3,52) kg, p=0,020], massa muscular esquelética [14,54 (2,38) vs 13,38 (1,95) kg, p=0,013], CMO do corpo total [1,945 (0,325) vs 1784 (0,265) g, p=0,005], DMO de corpo total [1,039 (0,109) vs 0,988 (0,090) g/cm2, p=0,011], DMO coluna lombar [0,983 (0,192) vs 0,903 (0,131) g/cm2, p=0,014], DMO colo de fêmur [0,813 (0,117) vs 0,760 (0,944) g/cm2, p=0,017] e DMO fêmur total [0,868 (0,135) vs 0,807 (0,116) g/cm2, p=0,026] significativamente maior quando comparado com pacientes que apresentavam consumo de proteína abaixo de 0,8g/kg/dia. Além disso, a ingestão de aminoácidos essenciais, principalmente os de cadeia ramificada como a valina [3,10 (0,89) vs 3,40 (1,04) g/dia, p=0,044] foi significantemente menor em mulheres com sarcopenia. O consumo de proteína se correlacionou positivamente com o índice de massa muscular esquelética (r=0,157; p=0,028) e a DMO do trocânter (r=0,185; p=0,010). Adicionalmente, a deficiência de vitamina D associados ao PTH elevado (> 65pg/dL), hiperparatiroidismo secundário, a prevalência de sarcopenia aumentada (77,1 vs 22,9%, p=0,032), além disso mulheres com hiperparatiroidismo secundário apresentaram massa muscular total [29,70 ( 2,99) vs 31,84 (3,65), p=0,043], índice de massa muscular esquelética [5,51 (0,55) vs 5,92 (0,78), p=0,043] significativamente menor. Alta prevalência de deficiência de vitamina D em mulheres com sarcopenia (71,4%). As mulheres com deficiência de vitamina D apresentaram massa muscular total [30,30 (2,92) vs 32,14 (3,84) kg, p=0,007], massa muscular esquelética apendicular [12,71 (1,59) vs 13,55 (0,82) kg, p=0,031]; índice de massa muscular esquelética [5,67 ( 0,60) vs 5,98 (0,82) kg/m2, p=0,030] e fêmur total BMD [0,791 (0,107) vs 0,838 (0,116) g/cm2, p=0,035] significativamente menor. Conclusões - A ingestão de proteínas acima 1,2g/kg/d, especialmente aminoácidos essenciais e suplementação de vitamina D deve ser considerada como terapia preventiva na redução da massa muscular e óssea em mulheres idosas / Introduction - Reduction of skeletal muscle mass, called sarcopenia, is associated with increased incidence of falls, fractures and functional dependence in the elderly. There are many factors that can contribute to the development of sarcopenia, among them the vitamin D deficiency and inadequate food intake, especially protein intake. Objectives - to investigate the relationship among sarcopenia, dietary intake and serum concentration of 25(OH)D. Methods - We evaluated 200 women over 65 years, 35 with sarcopenia and 165 without sarcopenia. Bone mineral density of lumbar spine, proximal femur and body composition (total muscle mass, skeletal muscle mass, fat mass, bone mineral content of the whole body) were assessed by Dual energy X-ray absorptiometry (DXA), radiological evaluation of the dorsal columns and lumbar (T4 to L4). Three-day dietary records were undertaken to estimate dietary intake and serum total albumin, calcium, phosphorus, creatinin, intact parathyroid hormone, 25(OH)D were measured. Results - Patients who presented protein intake above 1.2g/kg/day showed total muscle mass [33.94 (4.72) vs 31.87 (3.52) kg, p=0.020], muscle mass skeletal [14.54 (2.38) vs 13.38 (1.95) kg, p=0.013], total body BMC [1.945 (0.325) vs 1784 (0.265) g, p=0.005], total body BMD [1.039 (0.109) vs 0.988 (0.090) g/cm2, p=0.011], lumbar spine BMD [0.983 (0.192) vs 0.903 (0.131) g/cm2, p=0.014], femoral neck BMD [0.813 (0.117) vs 0.760 (0.944) g/cm2, p=0.017] and total femur BMD [0.868 (0.135) vs 0.807 (0.116) g/cm2, p=0.026] significantly higher when compared with patients who presented protein intake below 0.8g/kg/day. Essential amino acids intake, especially branched chain such as valine [3.10 (0.89) vs 3.40 (1.04) g/day, p=0.044] was significantly lower in women with sarcopenia. Protein intake positively correlated to skeletal muscle mass index (r=0.157, p=0.028) and trochanter BMD (r=0.185, p=0.010). Additionaly, presence of sarcopenia increases more than 20% when vitamin D deficiency is associated to PTH levels higher than 65pg/dL (77.1 vs 22.9%; p=0.032). Women with secondary hyperparathyroidism presented significantly lower total muscle mass [29.70 (2.99) vs 31.84 (3.65); p=0.043], SMMI [5.51 (0.55) vs 5.92 (0.78); p=0.043]. it was also observed high prevalence of vitamin D deficiency in women with sarcopenia (71.4%). Women with deficiency of vitamin D presented significantly lower TSMM [30.30 (2.92) vs 32.14 (3.84) kg; p=0.007], ASMM [12.71 (1.59) vs 13.55 (0.82) kg; p=0.031]; SMMI [5.67 (0.60) vs 5.98 (0.82) kg/m2; p=0.030] and total femur BMD [0.791 (0.107) vs 0.838 (0.116) g/cm2; p=0.035]. Conclusions Protein intake above 1.2g/kg/d, particularly essencial amino acids and vitamin D supplementation should be considered as preventive therapy in reducing muscle and bone mass in elderly women

As the rates of obesity continue to increase among adolescents and young adults, adopting healthy dietary and lifestyle habits is necessary in order to prevent obesity-related chronic disease later in life. Although several studies have addressed nutrition education and its effect on weight in college students, few studies have assessed percent fat as it relates to a semester-long nutrition course. As such, the effectiveness of a formal introductory nutrition course on lifestyle habits and percent fat of college students was examined. The current study aimed to address the relationship between percent body fat and nutrition education over the course of 8-months. Using a quasi-experimental design, this study compared changes among an intervention group and a comparison group pre-semester, post-semester and at 8-months follow-up. Participants completed a dietary habits survey and body composition was measured between August 2015 and May 2016. Results indicated that nutrition knowledge may have a short-term impact on dietary habits and body fat percentage among college-aged students. Between baseline and 4-months, we found a 1.9% reduction (27.29%-26.77%) in body fat percentage among the experimental group, while there was a 2.5% increase (25.25%-25.89%) in body fat percentage among the control group. Although we could not determine the exact reason, our results suggest that the reduction in body fat percentage may be due to knowledge and exercise. Our findings suggest that nutrition education has the potential to affect body composition among college students.

Objectives The purpose of this research was to describe the physical growth status, bone mineral content, areal bone mineral density, body composition, and metabolic risk level of children of Sudanese immigrant families, and to determine the relationship between these outcome measures and exposure to an adverse environment. Exposure was defined as the time spent in Sudan or neighboring countries and timing was defined as the age a child arrived in the USA. Two major modifying factors were considered; current nutritional status (food quality and food security) and current physical activity levels. Study Design and Methods This is a cross-sectional study conducted between July 2011 and April 2012. Subjects were recruited from the Iowa City, Iowa metropolitan area. The sample included 64 children between the ages of five and eighteen; 33 females and 31 males. Physical growth measures included weight, height, and BMI. Bone growth measures (body bone mineral content and areal bone mass density at the hip and spine) and body composition measures (lean mass, fat mass, and body fat percent) were measured using DXA. Metabolic risk factors included fasting blood glucose, low density lipoprotein (LDL), high density lipoprotein (HDL), total cholesterol, triglyceride, and C Reactive Protein (CRP) levels, and Homeostasis Model of Assessment Insulin Resistance (HOMA-IR). Physical activity was measured by self-report physical activity questionnaire for children and adolescents (modified PAQ-A and PAQ-C) and by direct measure using Omron Pedometers (HJ-720 IT). Other collected data included food quality, food security, food frequency, and pubertal development using a puberty developmental scale. Results The mean age for all children was 10.1 ± 3.3 years. More than half of the children (n=33, 51.6%) were born in the USA, 14 children (21.9%) were born in Sudan, and the other children were born in other countries. The majority of the children (63.6%) lived in low income households reporting annual income less than USD $19,000. Over one quarter (26.5%) of the children were overweight or obese as defined by BMI percentile and when categorized by BF%, 35.5% of the girls and 27.3% of the boys were identified as obese. Height stunting was noted with 4.7% severely stunted (more than 2 sd below the mean) and 9.4% moderately stunted (more than 1 sd below the mean). The mean Z score for FMI and LMI were -0.57 ± 1.51 and 0.49 ± 0.75, respectively, and neither was normally distributed. Around half of the children had FMIZ (53.1%) and LMIZ (47%) scores more than 1 SD below the mean. Median Z scores for all bone measures were negative; BMC, -0.71, hip aBMD, -0.53, and Spine aBMD, -0.13. Around one-third of the children fell more than 1sd below the mean for BMC (38%) and hip aBMD (33%). Metabolic risk factors were elevated in some subjects; high total cholesterol, 23.4%; high triglycerides, 32.8%; low HDL, 19%; high HOMA-IR and CRP levels, 15.6 %. Forty percent of participating families reported some level of food insecurity, and 31% reported skipping or cutting the size of meals due to inadequate food supplies. Both self-reported questionnaires and data collected from pedometers showed that the majority of study participants were inactive, Wednesday & Thursday were identified as the most active days with activity levels of 52.6% and 50.9%, respectively, and 40% of the study subjects were inactive on weekends. More than half (56.9%) of the subjects reported watching TV more than two hours per day. Children born in the USA had higher rates of height and weight stunting and obesity as compared to children born outside the USA (24%, 37.5%, 32.26%; 3.12%, 25%, 21.21%, respectively). Children born in the USA had lower Z scores in all bone and body composition measures. Using GEE analysis, longer residence in Sudan was associated with lower WAZ scores (β =-0.16, p= 0.07), and lower LMIZ scores (β =-0.05, p= 0.06). Children with longer residence in Sudan or neighboring countries had higher LDL and HOMA-IR levels (β =2.997, p= 0.0005), and (β =0.03, p= 0.08). Adjusting for gender, girls who spent more time in Sudan had higher triglyceride and CRP levels β =11.9, p=0.027) and (β =0.5, p=0.03), respectively. Children who were older when they entered the USA had higher HAZ scores (β =0.06, p=0.05). Adjusting for gender, Girls who arrived in the USA at a younger age had lower WAZ scores (β =-0.42, p=0.01), while girls who entered the USA at an older age had higher HOMA-IR, triglyceride, and CRP levels (β =0.29, p=0.005), (β =0.14, p= 0.05) and (β =0.5, p=0.05), respectively. Adjusting for number of years spent in the USA and physical activity levels, longer residence in Sudan was associated with poorer LMIZ (β =-0.06, p=0.001) and hip aBMD Z scores (β =0.11, p= 0.01). In addition, children who arrived in the USA at a younger age had higher height for age Z scores (β=0.094, p=0.005) and lower LMIZ scores (β =-0.09, p=0.04), respectively. Conclusion Sudanese children in the Iowa City metropolitan area, particularly those born in the USA, have low Z scores for physical growth, bone growth, and body composition measures. A significant percent of the children had high triglycerides and total cholesterol levels. The majority of Sudanese children were physically inactive and food insecurity was common.

Widespread increases in the prevalence of childhood obesity have raised the prospect of serious public health consequences in many countries. New Zealand is no exception; according to the most recent national estimates, approximately one in three children is overweight or obese. As a consequence, an understanding of the specific risk factors that predict this condition in children is becoming increasingly important. It is generally accepted that the promotion of physical activity is a key strategy for reducing the risk of childhood obesity. However, there is limited information describing physical activity and its relationship with body fatness in young New Zealanders. The overall aim of this thesis was to gain insight into the associations between excess fatness and physical activity in New Zealand children from a diverse range of socio-demographic groups. Three related studies were conducted to achieve this aim: a large descriptive survey of obesity and physical activity patterns in primary-aged children, and two preceding studies which develop the methodology for objective assessment of physical activity in this population. The first study provided the only validation data for the NL-2000 multiday memory (MDM) pedometer in children. In a sample of 85 participants aged 5-7 and 9-11 years, the NL-2000 offered similar accuracy and better precision than the widely used SW-200 pedometer (NL-2000: mean bias = -8.5 ± 13.3%; SW-200: mean bias = -8.6 ± 14.7%). The second study investigated reactivity to wearing pedometers over four 24-hour testing periods in 62 children aged 5-11 years. The sample was divided into two groups: one was given a full explanation of the function of the pedometer, while the other received no information prior to testing. The absence of significant differences in step counts between the first and last test periods indicated that there was no evidence of reactivity to this device for either preparation procedure. The central study presented in this thesis was the measurement of physical activity, body composition, and dietary patterns in 1,226 children aged 5-12 years, from which four chapters (4-7) were derived. The sample was ethnically diverse, with 46.8% European, 33.1% Polynesian, 15.9% Asian, and 4.1% from other ethnicities. Physical activity levels over three weekdays and two weekend days were assessed using NL 2000 pedometers. Percentage body fat (%BF) was determined using hand-to-foot bioelectrical impedance analysis with a prediction equation previously developed for New Zealand children. Waist and hip girths, height, and weight were measured using standard anthropometric techniques. Parent proxy questionnaires were used to assess demographic and lifestyle factors and pedometer compliance. The first reported analyses of this dataset (Chapter 4) examined the effect of weather conditions on children’s activity levels. In boys, a 10ºC rise in ambient temperature was associated with a 10.5% increase in weekday steps and a 26.4% increase in weekend steps. Equivalent temperature changes affected girls’ step counts on weekdays only (16.2% increase). Precipitation also had a substantial impact, with decreases in weekday and weekend step counts during moderate rainfall ranging from 8.3% to 16.3% across all sex, age, and socioeconomic (SES) groups. The aim of Chapter 5 was to understand the relationship between children’s step counts and their body mass index (BMI), waist circumference (WC), and %BF. Mean step counts for this sample were 16,133 ± 3,864 (boys) and 14,124 ± 3,286 (girls) on weekdays, and 12,702 ± 5,048 (boys) and 11,158 ± 4,309 (girls) on weekends. Significant associations were detected between steps.day-1 and both WC and %BF, but not between steps.day-1 and BMI. The findings in Chapter 6 extended these results by estimating the number of steps required to reduce the risk of excess adiposity in children (16,000 and 13,000 steps.day-1 for boys and girls, respectively). Finally, the study described in Chapter 7 examined the associations between excess adiposity and a series of demographic and lifestyle variables, providing the first assessment of body fat correlates in young New Zealanders. Our results indicated that children aged 11-12 years were 15.4 times more likely to be overfat (boys, %BF ≥ 25%; girls, %BF ≥ 30%) than those aged 5-6 years. In addition, the odds of overfat were 1.8 times greater in Asian children than in European children, and 2.7 times greater in the low SES group when compared with the high SES group. Three modifiable behaviours related to fat status were also identified: low physical activity, skipping breakfast, and insufficient sleep on weekdays. Clustering of these risk factors resulted in a cumulative increase in the prevalence of overfat.

Protein wasting is a complication of glucocorticoid (GC) therapy. It causes substantial morbidity and there is no treatment. This thesis investigates the metabolic mechanisms underlying GC-induced protein wasting and the potential for anabolic hormones to reverse protein loss. The models of GC excess were Cushing's syndrome and GC therapy. Whole body protein metabolism was assessed using the leucine turnover technique and body composition by dual-energy X-ray absorptiometry to estimate lean body mass (LBM) and fat mass (FM). As previous studies demonstrated that LBM and FM influenced rates of protein metabolism, the magnitude of body compositional abnormality in Cushing's syndrome was determined. After accounting for the greater FM (30%) and lesser LBM (15%), protein metabolism in Cushing's syndrome was characterised by a significant increase in protein oxidation, an abnormality that leads to irreversible protein loss. Successful treatment of Cushing's syndrome normalised protein oxidation. Studies of the acute and chronic effects of therapeutic GCs revealed a time-dependent effect on protein metabolism. GCs acutely increased protein oxidation. However, the rate of protein oxidation during chronic therapy at a similar dose was not significantly different to untreated control subjects. This time-dependent change suggests that GC-induced stimulation of protein oxidation does not persist and could represent a metabolic adaptation to limit protein loss. This finding contrasts with that in Cushing's syndrome, where protein oxidation is persistently elevated. This difference may represent a dose effect. Studies in GH-deficient subjects revealed that GH induced a fall in protein oxidation that was significantly correlated with a subsequent gain in LBM. This suggests that the anabolic potential of a therapeutic substance can be predicted by its ability to suppress protein oxidation acutely. Finally, the potential for GH and androgens to reverse the metabolic effects of GCs was assessed. A preliminary study in GC users revealed that a GH dose of 0.8 mg/d was effective in reducing protein oxidation. In a subsequent study, the GH-induced reduction in protein oxidation in women on GCs was enhanced by combined treatment with dehydroepiandrosterone, an androgen. In summary, GCs induce protein loss by stimulating protein oxidation. GH reverses this effect and this action is enhanced by coadministration of androgens. GH and androgens may be used therapeutically to prevent protein loss induced by GCs.

Doctor of Philosophy (PhD) / Introduction: The conventional approach to weight loss, recommended by almost all health authorities around the world, has been to reduce the total amount of fat in the diet and replace with carbohydrates. However, research trials using this approach have produced only modest results at best, and despite the active promotion of low fat eating and an apparent decline in fat consumption, rates of overweight and obesity have continued to climb. More recently low glycaemic index (GI) and high protein diets have become popular and are widely used by the public. However, only a small number of randomised controlled trials have been conducted and none directly comparing the two. Both approaches effectively reduce glycaemic load (GL) and aim to reduce post-prandial glycaemia and insulinaemia. This study aimed to evaluate the ability of diets with reduced GL to enhance the weight loss effects of a reduced-fat diet, to compare the two approaches of reducing GL on metabolic and anthropometric changes, and to investigate any benefit of combining both approaches to produce the lowest GL. Methods: We conducted a 12-week intervention in 129 overweight or obese young adults who were assigned to one of four diets with varying GL, protein, carbohydrate and GI, but similar fat (30% energy), fat type and fibre content. DIET 1 (highest GL) contained 55% E as carbohydrate; DIET 2 was a low-GI version of DIET 1; DIET 3 was a high protein diet with 25% E as protein; DIET 4 (lowest GL) was a low-GI version of DIET 3. The increase in protein in DIETS 3 and 4 came primarily from lean red meat. All key foods and some pre-prepared frozen meals were provided to maximise dietary compliance. Outcome measures were body weight, body fat, lean mass, waist circumference and the following blood parameters: total cholesterol, LDL-cholesterol, HDL-cholesterol, triacylglycerols (TAG), free fatty acids, C-reactive protein, fasting insulin, fasting glucose and leptin. Insulin resistance and β-cell function were assessed using homeostatic model assessment (HOMA) and the newer computer models HOMA2-insulin sensitivity and HOMA2-β-cell function. Results: While all groups lost similar amounts of weight (4.2 to 6.2% of initial weight, p=0.09), the proportion who lost >5% of body weight varied significantly by diet: 31%, 56%, 66% and 33% in groups 1, 2, 3 and 4 respectively (p=0.011). Differences were strongest in women (76% of the total group) who showed significant differences among groups in percentage weight change (-3.7 ± 0.6%, -5.7 ± 0.6%, -6.5 ± 0.5%, -4.1 ± 0.7% respectively, p=0.005) and fat loss (-3.1 ± 0.4kg, -4.9 ± 0.6kg, -4.8 ± 0.4kg, -3.6 ± 0.7kg respectively, p=0.007). Total and LDL-cholesterol increased on DIET 3 (high protein) compared to a fall on diet 2 (high carbohydrate/low-GI, p=0.013). TAG, HDL-cholesterol and glucose homeostasis improved on all four diets, with no effect of diet composition. Goals for energy distribution were not achieved exactly: both carbohydrate groups ate less fat and the diet 2 group ate more fibre. Conclusions: Reducing GL, through either substituting low-GI foods or replacing some carbohydrate with protein, improved the efficacy of a reduced-fat diet in women and in those with high TAG. Combining both approaches to produce the lowest GL did not promote further weight or body fat loss. Although weight loss was similar in all four diets for the group as a whole, overall clinical outcomes were superior on the high carbohydrate, low-GI diet.

The role of dietary fatty acids and their subsequent effects on metabolism has received considerable attention in mammalian species. It is becoming increasingly clear that fatty acids have metabolic roles over and above their influence on energy density of the diet. Recent studies have linked changes in the fatty acyl composition of the plasma membrane, induced by the dietary fat profile, to alterations in both lipid and glucose metabolism. These dietary induced changes have profound effects on insulin action, glucose transport and enzyme activity that regulate triglyceride and fatty acid synthesis, factors that ultimately influence protein and lipid deposition of animals. Because of their high growth rate, broiler chickens have a high requirement for energy and the use of triglycerides as a major energy source has resulted in a fat carcass. A change in the glucose-insulin balance has been suggested as being the main reason for differences in adiposity between broilers selected for fatness or leanness. The hypotheses of this thesis is based on the finding that dietary polyunsaturated fatty acids (PUFA�s) increase the sensitivity of muscle tissue to insulin and this would presumably augment insulin-stimulated glucose uptake into muscle cells. Therefore, increasing the capacity of broiler muscle tissue to utilise glucose as its principal energy substrate would reduce the bird�s reliance on triglycerides and this inturn would result in a leaner carcass. The aims of this study are firstly to explore the role that dietary PUFA�s from the n-3 and n-6 series have on the growth and body composition of broiler chickens and secondly to determine the relationships between dietary fatty acid profile, tissue insulin sensitivity and lipid deposition. Because dietary fatty acids have been implicated in the modulation of hormones important for the growth and development of animals, a third aim of this thesis is to determine the effects of dietary n-3 and n-6 polyunsaturated fatty acids on pituitary and adrenal sensitivity. Since the modulation of metabolism by dietary fatty acids has been attributed to changes in the fatty acyl composition of the plasma membrane, the final aim of this study will be to investigate and characterise the molecular species of the breast muscle choline and ethanolamine phospholipids. Feeding either fish oil a source of n-3 PUFA�s or sunflower oil a source of n-6 PUFA�s fatty acids to broiler chickens resulted in a significant (P<0.01) reduction in the abdominal fat pad mass and a modest increase in breast muscle mass when compared to broilers fed edible tallow. Associated with the changes in carcass composition was an alteration in energy substrate utilisation. This was reflected by lower respiratory quotients and reduced triglyceride and insulin concentrations for the chickens fed the two PUFA diets. Coupled to the shift in energy metabolism was a significant (P<0.05) increase in the proportion of PUFA�s incorporated into the abdominal fat pad and breast muscle. The dietary fat supplements resulted in the incorporation of specific fatty acid subtypes. Feeding fish oil significantly increased the proportion of long-chain n-3 PUFA�s whereas feeding sunflower oil significantly increased the proportion of long-chain n-6 PUFA�s compared to tallow feeding whose tissues were dominated by a higher proportion of saturated fatty acids. It was further shown that dietary n-3 and n-6 PUFA�s enhanced glucose /insulin action. Feeding either fish oil or sunflower oil to broiler chickens increased insulin action when examined by an intravenous glucose tolerance test. The maximal insulin release in response to the glucose infusion was higher in the tallow fed group compared to either the sunflower oil or fish oil groups. To estimate the disappearance rate of glucose from the plasma and its incorporation into tissues, 2-deoxy-D-3H glucose was infused into each chicken. There were no significant differences in the clearance rate of 2-deoxy-D-3H glucose from the plasma. However, when measured under steady state conditions, the labelled glucose incorporation into the breast muscle was greater in birds fed fish oil compared to either tallow or sunflower oil feeding. The dietary fatty acid induced increase in insulin action suggests that the sensitivity of muscle cells to insulin was enhanced. This modulation of tissue sensitivity by dietary fatty acids was also shown to occur at the level of the pituitary. To provide an estimate of pituitary sensitivity, bolus GnRH and GHRH infusions were given on different days to chickens fed the three dietary treatments. Feeding sunflower oil (n-6 PUFA�s) increased the level of GH that was released in response to the GHRH infusion when compared to birds fed either tallow or fish oil (n-3 PUFA�s). This dietary fatty acid modulation appears to be specific to certain pituitary cell types as there was no effect on LH secretion following the GnRH infusion. Dietary fatty acid modulation of endocrine gland sensitivity is particular to the gland type. Although the dietary treatments mediated a distinct pattern in pituitary sensitivity to GHRH infusion, these same three diets did not influence adrenal sensitivity, as there was no difference in the corticosterone profile following either ACTH or CRF infusion. The previously observed physiological changes for the three dietary groups was expected to be positively correlated to an alteration of the plasma membrane phospholipids induced by the dietary fatty acids. Supplementation with fish oil (n-3 PUFA�s) significantly increased levels of both eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) into the choline (PC) and ethanolamine (PE) breast muscle phospholipids compared to either sunflower oil (n-6 PUFA�s) or tallow supplementation. The increase in n-3 PUFA incorporation was associated with a corresponding decrease in the proportion of arachidonic acid (AA; 20:4n-6) an event that would presumably alter substrate availability for the 1- and 2-series eicosanoids. However, feeding sunflower oil or tallow gave a molecular species profile that was remarkably similar in both fatty acid subtype and proportion. This suggests that the plasma membrane dynamics would be similar for these two dietary groups. Therefore, it is appears that factors other than a change in the fatty acyl- composition of the plasma membrane may be responsible for modifying the physiology of the broiler.

From conception the dynamic balance between nutritional and activity factors play a role in the accumulation of risk for future disease. Maternal nutrient balance and the subsequent dietary pattern of the family set the path for the growth and development of the individual and therefore also for their offspring. There is strong evidence from studies in India that mothers who have a low vitamin B12 status, but high folate, will have children with higher adiposity and more cardiovascular risk factors than those with adequate B12. The B12 status is closely linked to the dietary pattern particularly the consumption of red meat which has a high B12 content. In New Zealand there are an increasing number of Indian migrants. Vegetarianism is also practiced by an increasing number including young women. In addition, there is a high rate (up to 60%) of unplanned pregnancies in New Zealand. In the 1997 New Zealand National Nutrition Survey (NNS97) report, vitamin B12 intake appeared adequate for the New Zealand population and breakfast cereals were reported as one major dietary source of B12. Cereals in New Zealand however, were not fortified with B12 and there was an error in the FOODfile™ data entries for B12 in some cereals. The raw data of reported B12 intakes in the 24-hour diet recall (24HDR) of NNS97 was reanalysed at the individual level by subtracting the B12 derived from breakfast cereals and applying the 2005 revised estimated average requirement (EAR) value. The possible prevalence of B12 insufficiency was 2.4 times that originally reported by the NNS97, translating into a prevalence of up to 27% of the population sampled. This analysis was limited as it was not adjusted for day-to-day variance or to the New Zealand population. This apparently high prevalence of risk for inadequate B12 intake in the surveyed individuals required confirmation that the B12 intake from 24HDR and also a 7-day diet diary (7DDD) was a valid assessment of B12 status. The group of particular interest is women of childbearing age (18-50y) with a range of eating patterns. Thirty eight women aged 19-48y; 12 non-red-meat-eaters (5 Indians vs. 7 non-Indians) and 26 red-meat-eaters (1 Indian vs. 25 non-Indians) participated in this validation study. Anthropometry and hand-to-foot bioelectrical impedance (BIA) were measured on the same day as a 24HDR was recorded. Fasting serum lipids, glucose, haematological parameters, and serum B12, holotranscobalamin II (holo-TC II, a specific B12 biomarker), and folate concentrations were measured. Foods eaten and time spent in physical activity during the following 7 days were extracted from 7DDD and 7-day physical activity diary (7DPAD). There was no significant correlation between dietary intake (24HDR or 7DDD) and biomarkers for B12 status. Indians reported lower mean daily B12 intakes in 7DDD than non-Indians (1.6 vs. 4.5 μg/day, p<0.001) and this was confirmed by Indians’ significantly low serum B12 (203 vs. 383 pmol/L, p=0.04) and holo-TC II (35 vs. 72 pmol/L, p=0.02) concentrations compared to non-Indians. A similar pattern was found between non-red-meat-eaters and red-meat-eaters in daily B12 intake in 7DDD (2.3 vs. 4.8 μg/day, p<0.001) and in B12 biomarkers (serum B12, 263 vs. 397 pmol/L, p=0.01; holo-TC II, 43 vs. 77 pmol/L, p<0.005). Non-red-meat-eaters reported significantly higher daily folate intake in 7DDD (359 vs. 260 μg/day, p=0.01) than red-meat-eaters but no significant difference was found in serum folate concentration between these groups (29 vs. 24 pmol/L, p=0.10). Indians/non-red-meat-eaters also reported lower daily protein intake and higher percentage of total energy from carbohydrate in 7DDD compared to non-Indians/red-meat-eaters but total reported energy intake tended to be under-reported and physical activity over-reported when assessed against estimated basal metabolic rate (BMR). Body composition varied by dietary pattern. Indians/non-red-meat-eaters had higher body fat percentage (BF %) and weaker grip strength than non-Indians/red-meat-eaters. In addition, Indians had a significantly higher waist-to-hip ratio (WHR) than non-Indians. Overall, the whole group reported that they were inactive. The median time spent in moderate, high and maximal intensity activities was only 19 minutes a day, which did not meet the NZ guideline for adults of 30 minutes a day. In this small study nutrient analysis of diet by 24HDR or 7DDD, was not a reliable or accurate way to assess B12 insufficiency. Questions about dietary patterns such as “do you eat red meat”, and taking ethnicity into account could more easily identify the at risk population. Supplementation and/or fortification of B12 should be considered before pregnancy.

Thesis (M.Sc. (Nutrition))--North-West University, Potchefstroom Campus, 2007.