Effect of physical exercise on glycogen turnover and net substrate utilization according to the nutritional state.
To determine the metabolic effects of a single bout of exercise performed after a meal or in the fasting state, nine healthy subjects were studied over two 8-h periods during which net substrate oxidation was monitored by indirect calorimetry. On one occasion, exercise was performed 90 min after ingestion of a meal labeled with [U-13C]glucose [protocol meal-exercise (M-E)]. On the second occasion, exercise was performed after an overnight fast and was followed 30 min later by ingestion of an identical meal [protocol exercise-meal (E-M)]. Energy balances were similar in both protocols, but carbohydrate balance was positive (42.2 +/- 5.1 g), and lipid balance was negative (-11.1 +/- 2.0) during E-M, whereas they were nearly even during M-E. Total glycogen synthesis was calculated as carbohydrate intake minus oxidation of exogenous 13C-labeled carbohydrate (calculated from 13CO2 production). Total glycogen synthesis was increased by 90% (from 47.6 +/- 3.8 to 90.7 +/- 5.4 g, P < 0.0001) during E-M vs. M-E. Endogenous glycogen breakdown was calculated as net carbohydrate oxidation minus oxidation of exogenous carbohydrate and was increased by 44% (from 35.8 +/- 5.6 to 51.7 +/- 6.6 g, P < 0.004) during E-M. It is concluded that exercise performed in the fasting state stimulates glycogen turnover and fat oxidation.
Schneiter
P
P
Institute of Physiology, Faculty of Medicine, University of Lausanne, Switzerland.
Di Vetta
V
V
Jéquier
E
E
Tappy
L
L
D000328:Adult; D002153:Calorimetry, Indirect; D050260:Carbohydrate Metabolism; D004435:Eating; D004734:Energy Metabolism; D005215:Fasting; D005260:Female; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D050356:Lipid Metabolism; D008297:Male; D009752:Nutritional Status; D010084:Oxidation-Reduction; D005082:Physical Exertion
D006003:Glycogen