Tarnopolsky, M. A., Atkinson, S. A., Phillips, S. M., & MacDougall, J. D. (1995). Carbohydrate loading and metabolism during exercise in men and women. Journal of Applied Physiology, 78, 1360-1368.

At an exercise intensity of 65% VO2max, women oxidize more lipids, and therefore decrease carbohydrate (CHO) and protein oxidation, compared with men. This investigation assessed the effects of trained state and increased carbohydrate intake on this phenomenon.

Similarly trained endurance athletes (M = 7; F = 7) were subjected to an increase in dietary CHO from 55-60 to 70% of energy intake for a period of 4 days (carbohydrate-loading).

Men increased muscle glycogen by 41% and performance at 85% VO2max by 45% whereas women showed no change in glycogen and performance improved only by 5%. During exercise at 75% VO2max, women oxidized significantly more lipid and less CHO and protein than men.

Implication. Endurance trained women do not respond to CHO-loading. It is a male phenomenon mainly caused by females' capacity to use fat as fuel while at similar exercise intensities males use CHO and proteins.

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