Doctor of Philosophy

dissertationThe purpose of this study was to determine whether 12 weeks of high dose (26 kcal/kg/week) or low dose (13 kcal/kg/week) endurance exercise is more efficacious for losing body weight, fat mass, and waist circumference and for temporarily elevating resting energy expenditure (REE) after a single bout of exercise in healthy yet sedentary, overweight, premenopausal women. Twenty-four volunteers were randomly assigned to either a high or low dose of exercise and completed 12 weeks of endurance training. Twelve-week changes in body weight, body composition, and waist circumference were not different between high dose and low dose exercise groups. Additionally, there were no group differences for change in postexercise REE (19-hour to 43-hour REE) after a single bout of prescribed exercise (5.2 kcal/kg versus 2.6 kcal/kg). However, there was substantial individual variability in the change in body weight (-3.9 to +3.2 kg), fat mass (-4.1 to +4.2 kg), waist circumference (-5.0 to + 3.3 cm), and postexercise REE (-341.0 to +645.4 kcal/day) in response to exercise training. Correlational analyses determined that average exercise energy expenditure accounted for 25% and 31% of the variability in the change in fat mass and waist circumference, respectively. Average exercise energy expenditure also accounted for 24% of the variability in 19-hour postexercise REE. Nineteen-hour postexercise REE was found to account for 25% and 35% of the variability in the iv change in fat mass and waist circumference, respectively. Nineteen-hour postexercise REE also accounted for 26% of the variability in the change in fat-free mass. In post hoc analyses, subjects were classified as exercise dose achievers or nonachievers. By definition, achievers were those participants who were able to sustain 13 kcal/kg/week for the final 5 weeks of training. When compared to nonachievers, achievers had greater reductions in fat mass (p= 0.03), waist circumference (p< 0.01), and body mass index (p=0.03). Moreover, achievers had an 18.1% higher 19-hour postexercise REE (p=0.03) as compared to nonachievers. These results suggest that the success of a given exercise prescription to elicit body weight and body composition improvements may depend on its ability to elicit increases in postexercise metabolic rate