Oral [13C]glucose oxidation during prolonged exercise after high- and low-carbohydrate diets

during prolonged exercise after high- and low-carbohydrate diets. J. Appl. Physiol. 85(2): 723–730, 1998.—The effect of a diet either high or low in carbohydrates (CHO) on exogenous 13C-labeled glucose oxidation (200 g) during exercise (ergo-cycle: 120 min at 64.0 6 0.5 % maximal oxygen uptake) was studied in six subjects. Between 40 and 80 min, exogenous glucose oxidation was significantly higher after the diet low in CHO (0.63 6 0.05 vs. 0.52 6 0.04 g/min), but this difference disappeared between 80 and 120 min (0.71 6 0.03 vs. 0.69 6 0.04 g/min). The oxidation rate of plasma glucose, computed from the volume of 13CO2 produced the 13C-to-12C ratio in plasma glucose at 80 min, and of glucose released from the liver, computed from the difference between plasma glucose and exogenous glucose oxidation, was higher after the diet low in CHO (1.68 6 0.26 vs. 1.41 6 0.17 and 1.02 6 0.20 vs