Effects of dietary composition and exercise timing on substrate utilization and sympathoadrenal function in healthy young women.
The effects of dietary composition (high-fat [FAT] or high-carbohydrate [CHO]) and exercise timing (preprandial exercise [Ex-] or postprandial exercise [-Ex]) on postprandial substrate utilization and sympathoadrenal function were studied in seven women aged 20 to 21 years. The experimental protocol included four different sessions (Ex-FAT, FAT-Ex, Ex-CHO, and CHO-Ex). The FAT and CHO diets provided 48% and 5% fat, respectively. On the experimental days, subjects ate a meal containing the same caloric energy at lunchtime, and they exercised for 30 minutes on a bicycle ergometer at an intensity of 60% maximal oxygen consumption (VO2max) before and after the meal, followed by rest for 3 hours. The resting respiratory quotient (RQ) was significantly lower (P < .05) with the FAT diet or postprandial exercise. The mean RQ during the experimental period was 0.78, 0.75, 0.81, and 0.77 in Ex-FAT, FAT-Ex, Ex-CHO, and CHO-Ex groups, respectively. The total area under the curve of serum norepinephrine (NE) as an index of NE secretion was significantly higher (P < .05) with the FAT diet or postprandial exercise (130.2, 175.8, 33.0, and 136.9 ng x mL(-1) x min, respectively). A negative correlation was observed between the RQ and the total area of NE (r = .49, P < .05). The serum thyroid hormone level was not influenced by dietary composition and exercise timing. These results suggest that postprandial exercise, especially after intake of a FAT diet, increases fat utilization via a slightly larger decrease in the RQ. This might be related to the sympathoadrenal system at rest and during exercise.
Matsuo
T
T
Division of Nutrition and Biochemistry, Sanyo Women's College, Hiroshima, Japan.
Suzuki
M
M
D000311:Adrenal Glands / Q000502:physiology*; D000328:Adult; D004032:Diet; D004435:Eating; D004837:Epinephrine / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D009638:Norepinephrine / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D012016:Reference Values; D013564:Sympathetic Nervous System / Q000502:physiology*; D013974:Thyroxine / Q000097:blood; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood
D014284:Triiodothyronine; D013974:Thyroxine; D009638:Norepinephrine; D004837:Epinephrine