Thesis (M.S.)--Brigham Young University. Dept. of Nutrition, Dietetics, and Food Science, 2003. / Includes bibliographical references (p. 58-62).

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Within nutrigenomics, clustering using data generated by microarray gene expression profiles can be used to identify sub-populations of subjects that respond differently to a given diet intervention. The use of clustering analyses is promising in obesity-related research as personalized nutrition is gaining popularity. This thesis focuses on clustering a human subcutaneous adipose tissue gene expression data set obtained during a low-calorie diet intervention to aid in the prediction of 6-month weight loss maintenance. The aims of the study were (1) to identify the best performing clustering method for clustering samples, (2) to identify differential responders to the low-calorie diet, and (3) to identify the biological pathways affected during the low-calorie diet by weight maintainers and weight regainers. MCLUST performed the best when clustering samples using relative weight change and either fasting insulin or insulin resistance change. Furthermore, it identified differences in the regulation of pathways between weight maintainers and regainers.

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We questioned whether adrenergic amines extracted from the Seville orange Citrus Aurantium (CA) increases metabolic rate and enhance the thermic response to a 1.7MJ mixed meal (TEF) in lean and obese men and women; the latter had upper-body obesity, a condition associated with defective TEF, attributed to altered SNS. Nine lean (7M, 2F; BMI: 23 +/- 1 k g/m 2; waist circumference: 78 +/- 2 cm) and 13 obese (4M, 9F; BMI: 35 +/- 1 kg/m2; waist circumference: 105 +/- 3 cm) subjects were studied. With CA: (1) RMR increased more in men vs women (94 vs 42 kJ over 5 h), independently of body composition; (2) urinary epinephrine excretion increased in both groups and dopamine only in men. A 17% lower TEF in obese subjects was no longer significant when controlled for gender. By contrast, there was an effect of gender on TEF that remained significant when adjusted for measures of obesity. Women had a lower TEF that increased to values no longer different from men with CA. CA did not affect TEF in men. CA had no cardiovascular effects. Thus, CA ingestion increased thermogenesis by 4% above RMR and enhanced the lower TEF of women by 29% (46kJ).

Our first objective was to compare deuterium incorporation and mass isotopomer distribution analysis in the measurement of in vivo cholesterol biosynthesis in humans. Twelve healthy subjects were recruited to participate in a 24 h stable isotope infusion study which mimicked temporal conditions typical of both deuterium incorporation and mass isotopomer distribution analysis techniques. Data suggest both deuterium incorporation and mass isotopomer distribution analysis accurately define cholesterol synthesis in humans when measured over a period of 24 h. / Our second objective was to examine the effects of weight loss through energy restriction upon human in vivo circulating cholesterol concentrations and synthesis using the deuterium incorporation methodology. Seven overweight subjects with a mean BMI of 30.6 +/- 1.6 kg·m-2 were recruited into a 2-phase prospective clinical trial including 3 mo on a weight stable American Heart Association Step I diet and 6 mo on an energy-reduced American Heart Association Step I diet. Data suggest that deuterium incorporation and mass isotopomer distribution analysis are equally effective methods for measuring cholesterol biosynthesis in humans, and that energy restriction resulting in modest weight loss effectively reduces endogenous cholesterol synthesis thus decreasing the risk of CVD development in obese and overweight men. (Abstract shortened by UMI.)

It is estimated that approximately 80% of all persons with DM2 are obese, and the prevalence of diabetes increases With increasing age and body weight. Intensive control resulting in near-normal glycemia in obese DM2 holds great potential for reducing morbidity and mortality, but is associated with weight gain. In turn, modest weight loss improves glycemia considerably. Current weight loss programs, with decreasing frequency of interventions over time, result in a weight loss pattern of a U-shaped curve indicating an inability in maintaining the lower weight. We hypothesized that increasing vs decreasing frequency of treatment visits over time would result in better weight loss and metabolic control. Forty-eight DM2 subjects (28 F, 20 M; wt = 98 +/- 3 kg; BMI = 35 +/- 2 kg/m2; DM duration = 11 +/- 8 yrs) were stratified according to weight and level of glycated hemoglobin (HbA1c), and randomized to one of two protocols: decreasing frequency (DF) of visits, seen weekly (for 2 mos), bimonthly (for 3 mos) and monthly (for 3 mos) and increasing frequency (IF) of visits seen in the reverse order. Visits included 18 lifestyle, behaviour modification, group sessions and 5 individual evaluations at 0, 2, 4, 8 and 12 months. (Abstract shortened by UMI.)

The purpose of this study was to examine weight loss methods and to determine if seasonal differences existed in energy and nutrient intakes, supplement use and eating behaviors of high school wrestlers. Weight loss history, food and activity records, supplement use and knowledge and bulimic behavior data were collected from twenty wrestlers during the 1998-99 wrestling season and from eleven wrestlers 3 months post wrestling season.This study found that wrestlers practiced extreme weight control behaviors including fasting, food and fluid restriction resulting in inadequate nutrient intakes. No significant seasonal differences were found in energy balance, nutrient intake or supplement use for this study group. There was a significant difference in bulimic behavior post season as compared to peak season, though no wrestler approached the cutoff score for clinical diagnosis of bulimia nervosa.Given the negative effects of extreme weight loss practices and inadequate nutrient intake on performance, nutrition education remains crucial for high school wrestlers. Further research using instruments to measure restrictive behaviors (as was practiced by subjects in this study) would be beneficial. Additionally future studies are needed to continually assess this population of athletes to gauge if changes in extreme behaviors are occurring. / Department of Family and Consumer Sciences

Twelve highly trained collegiate wrestlers were studied to determine if performance of a six-minute arm crank task can be maintained by feeding a hypocaloric, high percentage carbohydrate diet to athletes during a four day weight loss period. Subjects were placed on a hypocaloric, low percentage (41.9%) carbohydrate diet (LC) and a hypocaloric, high percentage (65.9%) carbohydrate diet (HC) during two separate weight loss periods. The reduction in work performed during six minutes of arm cranking from pre- to post-weight loss was 0.9% and 8.2% for HC and LC treatments, respectively. Post exercise lactate measures were significantly lower and pH values were significantly higher pre- and post-weight loss under the LC treatment as compared to the HC treatment. Pre-exercise glycerol values were significantly higher post weight loss as compared to pre weight loss under both diet treatments. Profile of Mood State (POMS) scores indicate a negative effect of weight loss on psychological well being of the subjects. This negative effect is exacerbated during weight loss under the LC as compared to HC treatment. These data indicate a significant reduction in performance following a four day weight loss of 6.1% under the LC treatment, while performance is maintained following the HC treatment. / Department of Biology