Date of Award

Fall 1981

Project Type

Dissertation

Program or Major

Psychology

Degree Name

Doctor of Philosophy

Abstract

The exact contributions of changes in thermogenesis to the energy balance of either rats or humans is not known. There is some evidence that differences in post-prandial heat production (dietary-induced thermogenesis), can explain why some individuals gain weight easily when overeating and others do not. There is also evidence that exercise enhances dietary-induced thermogenesis. However, it may be the effects of exercise training rather than the exercise itself which enhances dietary-induced thermogenesis. Aerobic exercise training may produce increases in dietary-induced thermogenesis and allow more calories to be expanded as heat when overeating.

In these three experiments, the effects of diet and exercise training on food intake, body weights, body composition, and thermogenesis was studied in male and female Sprague-Dawley weanling and adult rats.

Overeating and obesity was produced by giving rats a supermarket diet, and aerobic training was accomplished by forcing some of the animals to swim 2 hours/day.

Thermogenesis was measured by indirect calorimetry while animals were in chambers connected to a closed-loop system. Changes in aerobic capacity were not measured directly but were inferred from changes in an enzyme in muscles known to increase with aerobic training, citrate synthase. The resulting changes in body weight with the supermarket diet and daily exercise could not be explained by changes in food intake. Both early diet and exercise affected thermogenesis and changes in heat production were found to be important in explaining the body weight changes.

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