Substrate metabolism when subjects are fed carbohydrate during exercise
Horowitz, J.F.; Mora-Rodriguez, R.; Byerley, L.O.; Coyle, E.F.
American Journal of Physiology 276(5): E828-E835
1999
ISSN/ISBN: 0002-9513 PMID: 10329975 Document Number: 511790
This study determined the effect of carbohydrate ingestion during exercise on the lipolytic rate, glucose disappearance from plasma (Rd Glc), and fat oxidation. Six moderately trained men cycled for 2 h on four separate occasions. During two trials, they were fed a high-glycemic carbohydrate meal during exercise at 30 min (0.8 g/kg), 60 min (0.4 g/kg), and 90 min (0.4 g/kg); once during low-intensity exercise 3 mU/ml; P < 0.05) during the second hour of exercise when subjects were fed vs. when they were fasted slightly attenuated lipolysis (P < 0.05) but did not increase Rd Glc or suppress fat oxidation. These findings indicate that despite a suppression of lipolysis after carbohydrate ingestion during exercise, the lipolytic rate remained in excess and thus did not limit fat oxidation. Under these conditions, a reduction in fat oxidation was associated in time with an increase in glucose uptake. Reprinted by permission of the publisher.