Author and graduation date: Jennifer Imgrund EDMONDSON, October 1998

Committee members: Mark J. Kern (Chair), Audrey A. Spindler, Judy M. Price

Thesis title: The Effect of Diet and Exercise on Serum Leptin in Women

Leptin, the product of the obese (ob) gene, has been demonstrated to correspond with available body energy stored as fat in human beings. In spite of this relationship, leptin levels vary widely among individuals with comparable body compositions, suggesting that other factors may mediate leptin secretion. The purpose of this study to determine the effect of a high carbohydrate diet versus a high fat diet on serum leptin in minimally active women and the effect of submaximal exercise on serum leptin following these two dietary interventions. Eight women participated in two randomly assigned, 5-day isocaloric interventions, separated by at least 4 weeks. The high carbohydrate (HC) and high fat (HF) diets contained ratios of caloric contributions from carbohydrate, protein and fat of 73:14:13 and 48:14:38 respectively. After each dietary intervention, and following an overnight fast, subjects performed a 30 minute bout of cycle ergometry at 70% of maximal oxygen uptake (VO2max). Blood samples were collected both before and after exercise and serum leptin levels were determined by radioimmumoassay. No difference was found between serum leptin levels following the HF and HC diet interventions, and no significant diet by exercise interaction was detected. Submaximal exercise significantly (p=0.048) lowered serum leptin concentrations compared with baseline (pre-exercise) levels by 11.3% (HC) and 12.2% (HF). These results indicate that diet composition has no significant effect on circulating leptin, while submaximal exercise may enhance the fall in serum leptin following an overnight fast in minimally active women. Contradictory results from previous studies on the possible effects of exercise on circulating leptim suggest that more research in needed in this area.

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