EFFECTS OF DIETARY-COMPOSITION AND EXERCISE TIMING ON ENERGY-EXPENDITURE AND SUBSTRATE UTILIZATION IN HEALTHY-YOUNG WOMEN

Effects of dietary composition (high fat, FAT; or high carbohydrate, C HO) and exercise timing (preprandial exercise, Ex-; or postprandial ex ercise, -Ex) on postprandial energy expenditure and substrate utilizat ion were studied in seven women aged 19-20 years. The experimental pro tocol included four different sessions (Ex-FAT, ExCHO, FAT-Ex, and CHO -Ex). The FAT and CHO diets provided 48 and 5% as fat, respectively. O n the experimental days, subjects were fed a meal containing the same caloric energy at lunch time and they exercised for 30 min on a bicycl e ergometer at an intensity of 60% VO2max at pre- or post-meal followe d by rest for 3 h. The values of oxygen consumption were 1,559, 1,628, 1,526, and 1,557 ml . kg(-1). 4h(-1) in Ex-FAT, Ex-CHO, FAT-Ex, and C HO-Ex groups, respectively. Total levels of serum insulin were 7.6, 13 .7, 4.5, and 7.8 mu U . ml(-1). min . 10(-3), respectively. These resu lts suggest that preprandial exercise, especially before CHO diet inta ke, has an advantage for increasing oxygen consumption. This advantage might be related to rates of substrate (''futile'') cycling and insul inemic responses at rest and during exercise.