Author and graduation date: Heidi Denise BRODER, May 1997

Committee members: Mark J. Kern (Chair), Micheal J. Buono, Martha J. Shively

Thesis title: Title: Effects of a High Carbohydrate Versus High Fat Diet on Excess Postexercise Oxygen Consumption

Excess postexercise consumption (EPOC) is the term describing the elevation of the metabolic rate following a bout of exercise. Although a number of potential factors that may affect EPOC have been studied, the effects of varied dietary composition have not. This study was designed to examine the influence of high intake of carbohydrate versus high intake of fat on the levels of energy substrates in the blood, as well as the magnitude and duration of EPOC in minimally active women. Eight subjects participated in a randomized cross-over design of two 5 day dietary interventions, separated by at least 4 weeks. The ratio of energy contributions from carbohydrate, protein and fat were 73:14:13 for the high carbohydrate (HC) diet and 48:14:38 for the high fat (HF) diet. On the morning following each dietary intervention, and after an overnight fast, each subject performed a 30 minute bout of cycle ergometry at 70% of maximal oxygen uptake (VO2max). Baseline heart rate (HR), VO2, respiratory exchange ratio (RER), and temperature were measured for 10 minutes after a 30 minute seated rest prior to exercise and continuously during recovery until baseline VO2 was achieved. The criterion for reaching baseline was two consecutive 3 minute readings within 5% of the previously established baseline. Whole blood lactate and serum concentrations of free fatty acids (FFA) and glucose were assessed at rest and immediately following exercise. There were no significant differences in blood lactate or serum FFA or glucose concentrations between the diet groups at rest or following exercise. Duration of EPOC was similar for both the HC (19.2+ 9.0 min) and HF (15.0 + 4.8 min) diets (p>0.05), and there were no significant differences in the magnitude of EPOC between the HC or HF diets (9.4+3.9 and 7.9+ 3.1 kcal), respectively. The two dietary interventions also had no differential effect on postexercise HR or RER. There was a significant (p<0.05) difference in tympanic temperature during the recovery period after exercise, with the HC diet eliciting a higher temperature (35.2+ 0.7 degrees celcius) compared to the HF diet (34.5+ 0.5 degrees celcius). Overall, there were no significant findings with respect to the effect of dietary intake on resting or postexercise energy substrates or EPOC. In conclusion, the dietary and exercise conditions utilized in this study did not contribute to significant differences in the preexercise or postexercise metabolic responses assessed.

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