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The purpose of this investigation was to expand the evaluation of Normal Weight Obesity (NWO) and its association with insulin resistance using a nationally representative sample of U.S. adults. A cross-sectional study including 5,983 subjects was conducted. Body fat percentage was assessed using dual energy X-ray absorptiometry (DXA). Expanded Normal Weight Obesity (eNWO) categories (pairings of BMI and body fat percentage classifications) were determined by standard cut-points for BMI and the gender specific median for body fat percentage. Homeostatic Model Assessment-Insulin Resistance (HOMA-IR) levels were used to index insulin resistance. Mean ± SE values were as follows: BMI: 27.9 ± 0.2 (women) and 27.8 ± 0.1 (men); body fat percentage: 40.5 ± 0.2 (women) and 27.8 ± 0.2 (men); HOMA-IR: 2.04 ± 0.05 (women) 2.47 ± 0.09 (men). HOMA-IR differed systematically and in a dose-response fashion across all levels of the eNWO categories (F = 291.3, P < 0.0001). As BMI levels increased, HOMA-IR increased significantly and within each BMI category, higher levels of body fat were associated significantly with higher levels of HOMA-IR. Both high BMI and high body fat percentage are strongly related to insulin resistance. In this study, insulin resistance increased incrementally according to BMI levels primarily and body fat levels secondarily. Consequently, due to the costs associated with precisely measuring body fat, and the accuracy of using BMI independently, we recommend that BMI be used in its standard form to predict insulin resistance and not be supplemented with an estimate of body fat.

Excessive phosphorus (P) excreted by animals can affect water quality and cause eutrophication. Better understanding of factors that influence P utilization and excretion in horses may reduce the environmental impact of P. Two animal experiments were conducted that examined P excretion by horses. The efficacy of titanium dioxide as an external marker to calculate digestibility was studied concurrently with both animal experiments. Additionally, pasture P concentrations were evaluated over the growing season using near-infrared spectroscopy (NIRS). Experiment 1 examined P excretion by post-lactational mares fed a low P diet immediately prior to weaning compared to non-lactating controls fed an adequate P diet. Post-lactational mares excreted more P compared to controls. Experiment 2 compared P excretion in horses fed to lose, maintain, or gain weight. Horses fed to lose weight tended to excrete more fecal P compared to horses fed to gain weight and had increased markers of bone turnover. The efficacy of titanium dioxide for estimating fecal output from limited fecal grab samples was variable. Titanium dioxide may be useful in situations where many fecal samples are collected over 5 d, but may not be as accurate if one fecal grab sample is expected to be representative of fecal output. Experiment 3 focused on examining the changes in pasture mineral concentration over the season using NIRS. A discussion of how these results may inform equine P supplementation programs is included. Overall, the work in this dissertation suggests that factors that influence P excretion in the horse include the dietary availability of P, physiological status, and active weight change. These variables can be incorporated into feeding programs to meet horses’ needs more closely while minimizing P excretion in the environment.

In light of alarming rises in the prevalence of obesity worldwide, tackling the obesity ‘epidemic’ is now a national health priority in many countries. Increasingly, population measures that provide accurate estimates of body fatness in children are required. Body mass index (BMI), or weight standardised for height, remains the most cost-effective and practical tool in this regard. However, there is evidence that the association between BMI and body fatness is variable in children from different ethnic backgrounds. The primary aim of this thesis was to investigate the appropriateness of BMI thresholds for defining overweight and obesity in female children and adolescents from five diverse ethnic groups. Secondary objectives were to examine the associations between weight control practices and perceptions, and to compare objectively-measured physical activity levels with participation in active transport (AT). In order to achieve the primary aim stated above, it was necessary to obtain valid and reliable measures of body fat percentage (%BF) in a large sample of children. Bioelectrical impedance analysis (BIA) is well suited for this purpose, providing a portable and cost-effective means to estimate fat-free mass (and subsequently %BF). While equations exist for European, Maori, and Pacific Island children, findings from the preliminary study described in Chapter 2 demonstrate that there are no BIA equations appropriate for Chinese and Indian children. Given that these two groups are two of the fastest growing ethnicities in New Zealand, a new equation was developed that enables Asian girls to be included in future BIA research. The main study of this thesis involved a large-scale investigation of body composition in New Zealand’s five major ethnic groups (European, Maori, Pacific Island, East Asian, and South Asian). A total of 1,081 adolescent girls aged 11-16 years participated in the Girls’ Activity and Body Composition (ABC) Study. To extend the age range, data were combined with another study of 5-11-year-old New Zealand children (595 girls), coined the Body-Size and Steps in Children (BASIC) Study. Both studies measured BMI from height and weight, %BF from bio impedance measurements, and physical activity using sealed multiday memory pedometers over five consecutive days. A questionnaire was also administered to the adolescent-aged girls to gather data related to weight perceptions and practices. Initial analyses of the main dataset demonstrated that existing BMI definitions of overweight were relatively insensitive for predicting excess %BF in South and East Asian girls. Conversely, low specificity was observed for Pacific Island and Maori children. These findings provided the rationale for the second set of analyses: the development of BMI cut-off points that correspond to an equivalent level of %BF across all ethnicities. The adjusted BMI curves for overweight and obesity ranged from an average of 3.3 and 3.8 kg.m-2 (respectively) lower than international standards in South Asian girls to 1.5 and 1.9 kg.m-2 higher in Pacific Island girls. Clearly, the proposed changes will have significant effect on our estimates of overweight and obesity in this population group. Subsequent investigation revealed that many adolescent girls misclassify their weight status. However, the number of girls trying to lose weight exceeded those who perceived themselves as being overweight, with the magnitude of the difference dependent on ethnicity. It was concluded that interventions and educational campaigns that assist girls in recognising a state of excess body fat are a priority for all ethnic groups to ensure that behavioural changes necessary to combat widespread overweight and obesity are adopted. Finally, it was observed that the physical activity levels of the participants were significantly lower on weekends (9,528  4,407) than on weekdays (12,597  3,630). Furthermore, a consistent decline in daily step counts was observed with age: after adjustment for ethnicity and socioeconomic status (SES), girls in school years 9-10 achieved 2,469 (weekday) and 4,011 (weekend) fewer steps than girls in years 1-2. Daily step counts also varied by ethnicity, with Maori girls the most active and South Asian girls the least active. Overall, girls who used AT to and from school averaged 1,052 more weekday steps than those who did not use AT. These data suggest that adolescent-aged girls and girls of Asian descent are priority groups for future physical activity interventions, and that the promotion of AT in girls appears to be worthwhile.

Body fat, regional body fat and bone mineral mass, are linked to health conditions such as obesity and osteoporosis. The ethnic comparison of body composition may help to explain and understand the difference of health outcomes and health status in different ethnic groups. NZ Chinese is the largest Asian group in New Zealand, however, knowledge about health risks and body composition for NZ Chinese is very limited. Therefore, the aims of this thesis were: 1) To compare the relationships between body mass index (BMI) and percentage body fat (%BF) of European (M29, F37), Maori (M23, F23), Pacific people (M15, F23), and Asian Indian (M29, F25) (existing data) with NZ Chinese aged 30-39 years; 2) To compare fat distribution, appendicular skeletal muscle mass (ApSM), bone mineral density (BMD) and limb bone lengths across these five ethnic groups. A convenience sample of healthy NZ Chinese (M20, F23) was selected by BMI to cover a wide range of body fatness. Total and regional body fat, fat free mass (FFM) and bone mineral content were measured by whole-body Dual-energy X-ray absorptiometry (DEXA). The main study findings were: • For a fixed BMI, NZ Chinese had a higher %BF than European and less %BF than Asian Indian. At a %BF equivalent to a BMI of 30 kg.m-2 in Europeans (WHO threshold for obesity), BMI values for Asian Indian and NZ Chinese women were 5.8 and 2.2 BMI units lower than European, respectively, and for Asian Indian and NZ Chinese men, 8.2 and 3.0 BMI units lower. • Abdominal-to-thigh fat ratio of NZ Chinese was significantly higher than that of European (P<0.001) and similar to that of Asian Indian. NZ Chinese had a significantly higher central-to-appendicular fat ratio than both Asian Indian and European (P<0.001). NZ Chinese was centrally fatter than European and Asian Indian. • For the same height and weight, NZ Chinese had significantly less FFM (-2.1 kg, P=0.039) and ApSM (-1.4kg, P=0.007) than European. NZ Chinese had significantly more FFM (+3.2 kg, P=0.001) than Asian Indian and similar ApSM to Asian Indian. • For the same weight, NZ Chinese had a similar BMD as European for female and male. NZ Chinese male had a higher BMD (+0.07 g.cm-2, P= 0.001) than Asian Indian male. • Among the five ethnic groups, NZ Chinese had the shortest leg (-1.5cm, P=0.016) and arm bone lengths (-2.3cm, P=0.001) (measured by DEXA) for the same DEXA height. Therefore, the relationship between percent body fat and BMI for Asian Indian and NZ Chinese differs from Europeans and from each other, which indicates that different BMI thresholds for obesity may be required for these Asian ethnic groups. Given the relatively high percentage body fat, low appendicular skeletal muscle mass and high central fat to appendicular fat ratio of NZ Chinese aged 30-39 years demonstrated in this study, promotion of healthy eating and physical activity is needed to be tailored for NZ Chinese. The NZ Chinese community should be advised to keep fit, prevent limited movements in older age, and to prevent obesity and obesity-related diseases.

Regular aerobic exercise may reduce cardiovascular disease (CVD) risk in part by lowering the concentration of inflammatory markers such as C-reactive protein (CRP). While studies in diseased populations have shown significant decreases in CRP concentrations with regular aerobic training, little has been conclusively determined regarding the effects of aerobic training on CRP concentrations in apparently healthy, untrained populations who may not be adequately screened for CVD risk by traditional methods. PURPOSE: To examine the effects of a 17-wk half marathon training program (TP) on CRP concentrations, aerobic fitness, and body composition in apparently healthy, untrained men. METHODS: Twenty men (29.3 ± 1.0 yr, 37.0 ± 1.6 mL•kg-1•min-1 VO2max, 29.1 ± 1.8% body fat) registered as training subjects (TRN) in a 17-wk half marathon TP. An additional 22 men (27.8 ± 1.4 yr, 38.8 ± 1.0 mL•kg-1•min-1 VO2max, 26.8 ± 1.4% BF) served as controls (CON). Fasting blood samples were taken at four time points over the TP and were analyzed for CRP and interleukin-6 (IL-6) concentrations. Aerobic capacity (VO2max) and body fat (BF%) were measured before and after the TP. RESULTS: No significant changes in CRP (P=0.69) or IL-6 concentrations (P=0.73) were seen in TRN as a result of the TP despite significant improvements in VO2max (42.2 ± 1.9 ml•kg-1•min-1, P<0.0001), resting heart rate (P =0.004), BF% (P =0.03) and BMI (P =0.05). No significant changes in CRP, aerobic fitness, BMI or BF% were detected in CON over time. CONCLUSION: Moderate, long-term aerobic training does not appear to affect CRP concentrations in apparently healthy, untrained men despite significant improvements in BW, BF%, BMI, and VO2max.

Background: Over the past decade obesity has doubled in children aged 6-11 and tripled among adolescents aged 12-19. One trend that has coincided with this increased obesity prevalence is decreased meal frequency, which may impact blood sugar, meal size, cortisol release, insulin release, and appetite controls that include the release of leptin and ghrelin. Ultimately, these changes may result in a simultaneous lowering of the metabolic (i.e., fat-free) mass and a rising of the fat mass. Purpose: To assess food/beverage intake in a way that would determine if large deviations in energy balance (EB) during the day were related to body fat percent (BF%). Methods: Using an IRB-approved protocol, male and female children were assessed using NutriTiming® (NutriTiming LLC, 2011) software, which simultaneously assesses energy intake from consumed foods and beverages and energy expenditure from activities with different intensities. A 24-hour recall questionnaire and interview, with at least one parent present, was used to obtain data, which represented a typical school day. BF% was assessed using an 8-mode bioelectrical impedance segmental body composition analyzer (Tanita, Model BC-418). Statistical analysis was performed with SPSS (ver. 18). Results: A total of 16 children ranging in age from 8-14 years were interviewed. Due to incomplete data on 4 subjects, 12 subjects (6 boys; 6 girls ranging in age from 9-14 years; mean=11.41 ± 1.5) were included in the data analysis. Energy intakes averaged 1,984 ± 510 kcal; and energy expenditure averaged 1,689 ± 351 kcal. Average BF% was 24.3 ± 4.9. Using Spearman correlation and independent group t-test (with the mean energy balance as the cut-point) traditional end-of-day energy balance (24-hr energy in vs. 24-hr energy out) was not statistically associated with body fat %, and there was no difference in BF% between those above and below the end-of-day EB mean. However, more hours spent in an energy surplus (EB > 0) was significantly associated with lower body fat % (r=-0.914; PP

This research evaluated photonic imaging devices for assessment of body size and shape. In aim one, laser imaging measurements of circumference, volume, and % fat were examined in 70 women. Bland-Altman analysis indicated minimal error in girth of the waist and hip by laser imaging as compared to tape measure (95% limits of agreement for waist, -2.02-2.29 cm; hip, -3.39-2.90 cm). Volume by laser imaging was related to hydrodensitometry (r = 0.99, p < 0.01), and % fat estimates were not significantly different from hydrodensitometry or dual energy X-ray absorptiometry (DXA) (3.95 ± 1.74, 32.54 ± 1.28, and 35.86 ± 1.06, respectively, p > 0.05). In aim two, 120 adults were evaluated via stereovision imaging. Stereovision was significantly related to volume by air displacement plethysmography (ADP) and hydrodensitometry (R² > 0.99, p < 0.01). However, Bland-Altman analysis indicated variations in body fat between stereovision and ADP (95% limits of agreement, -16.77-16.05 kg). Therefore, aim three was development of a prediction equation to estimate fat from 13 stereovision measurements of body size and shape. These parameters combined to form upper and lower body factor scores, which, with gender, predicted 88.6% of variation in fat mass by ADP (p < 0.01). The equation improved 95% limits of agreement from -16.77-16.05 kg via direct volume measurement to -11.47-8.45 kg compared to ADP. Finally, in aim four, a subset of 56 women from aim two was evaluated for visceral fat by magnetic resonance imaging (MRI). Visceral fat was compared to a new indicator of abdominal adiposity via stereovision imaging: central obesity depth. Central obesity depth was correlated with visceral fat, following adjustment for age and ethnicity (r = 0.75, p < 0.01). Additionally, each 1 cm rise in central obesity depth raised the odds of being in the high versus low visceral fat tertile (Odds Ratio 8.59, 95% Confidence Interval 1.33-55.63, p < 0.05). Thus, both laser and stereovision body imaging appear to be valid techniques for evaluation of body size and shape. Furthermore, central obesity depth is a promising new measurement for assessment of visceral adiposity. / text

The Relationships Between Real Time Energy Balance, Hunger, and Body Composition Delk A, Benardot D, Nucci A, & Thompson WR. Georgia State University Introduction: Previous research has indicated that hunger is associated with the quantity, volume, and macronutrient composition of food intake. Hunger has never been assessed from the viewpoint of real time energy balance, although there is limited research on hunger and eating frequency. Purpose: The purpose of this study was to evaluate the relationships between real time energy balance, hunger, and body composition in college students between the ages of 18-30. Methods: Participants were assessed for body composition using a Tanita scale and energy balance was determined on an hourly basis using NutriTiming® software. A hunger scale was used to assess participant hunger every hour. Results: There is a statistically significant relationship for the entire population between energy balance average and body fat percent (R= -0.376; P=0.037). Hours spent in energy deficient is positively associated with body fat percent (R=0.467; P=0.008), while hours spent in an optimal energy balance is negatively associated with body fat percent (R= -0.465; P=0.009). Hours spent in an energy balance surplus (+400 kcals) were not significantly associated with body fat percent. However, hours spent in an anabolic state (>0 kcals) was negatively associated with body fat percent (R=-.457; P=.010). Conversely, hours spent in a catabolic state (<0 kcals) were positively associated with body fat percent (R=.457; P=0.10). Using linear regression analysis with body fat percentage as the dependent variables and age, height, weight, gender, and hours in optimal energy balance, we determined that we could predict a large amount of variance in body fat percentage (R= .931; P= <.001). The only time during the day that there was a significant correlation between body fat percent and hunger was at 5pm (R= -0.391, P = 0.029). Conclusions: These data suggest that that the more time spent in energy deficit is associated with a higher body fat percent. This should encourage college students between the age of 18-30 to avoid restrictive eating patterns and strive to maintain optimal energy balance in order to achieve a low body fat percent.

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