Abstract

Ten subjects were studied to determine the effects of medium chain triglyceride plus carbohydrate (MCT), long chain triglyceride plus carbohydrate (LCT), and carbohydrate (CHO) feedings on substrate utilization during 60 min of endurance exercise (70 V02max). Based on the respiratory exchange ratio, the percentage of energy obtained from lipid metabolism during the MCT, LCT, and CHO trials was similar (37.2 to 39.1). This, however, differed significantlyfrom the percentage of lipid metabolized (49.1) during the control (CONT) trial (fasted state). Serum glycerol paralleled the estimated lipid oxidation and was 74 higher in the CONT trial when compared to the MCT, LCT, and CHO trials by the end of exercise. Prior to exercise, glucoselevels were the samefor all treatments, but insulin levels for the three experimental trials were threefold higher than those of the CONT. After 15 min of exercise glucose levels had declined significantly in the experimental trials, while rising slightly during the CONT trial. Despite this hypoglycemic state, no differencein the perceived exertion was found between the experimental and CONT trials. These data indicate that hyperinsulinemia causes a perferential oxidation of carbohydrates during exercise even when other substrates (FFA and ketones) arepresent in elevated amounts. Verf.-Referat