תזונה ותוספים Carbohydrate Supplementation and Sex Differences in Fuel Selection during Exercise.

[Mike Bikov]

Med Sci Sports Exerc. 2009 Dec 14. [Epub ahead of print]
Carbohydrate Supplementation and Sex Differences in Fuel Selection during Exercise.

Tremblay J, Peronnet F, Massicotte D, Lavoie C.

1Department of kinesiology, University of Montreal, Montreal, QC 2Department of kinanthropology, University of Quebec in Montreal, Montreal, QC 3Department of exercise sciences, University of Quebec in Trois-Rivieres, Trois-Rivieres, QC.

PURPOSE:: To compare the effects of a high-CHO diet (80% as CHO) and glucose ingestion (2 g.kg) during exercise (120 min, 57% VO2max) on fuel selection in women taking (W+OC) or not (W-OC) oral contraceptives and in men (six in each group). METHODS:: Substrate oxidation was measured using indirect respiratory calorimetry in combination with a tracer technique to compute the oxidation of exogenous (C-glucose) and endogenous CHO. RESULTS:: In the control situation (mixed diet with water ingestion during exercise), the percent contribution to the energy yield (%En) of CHO oxidation was higher in men than in women (62 vs. 53 %En). The high-CHO diet and glucose ingestion during exercise separately increased the %En from CHO oxidation in both men (+12%) and women (+24%) and the sex difference observed in the control situation disappeared. However, the increase in the %En from total CHO oxidation observed when glucose was ingested during exercise and when combined with a high-CHO diet was larger in women than in men (+47 vs. +17 %En). This was not due to a higher %En from exogenous glucose oxidation in women, for which no sex difference was observed (25 and 27 %En in men and women), but to a smaller decrease in endogenous glucose oxidation. No significant difference in fuel selection was observed between W+OC and W-OC. CONCLUSION:: The increase in total CHO oxidation following the high-CHO diet was not different between sexes. Glucose ingestion during exercise, separately and combined to the high-CHO diet, had a greater effect in women than in men; this was mostly due to the smaller reduction in endogenous CHO oxidation.

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