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Carbohydrate supplementation and sex differences in fuel selection during exercise.
Jonathan Tremblay1, Francois Peronnet, Denis Massicotte
1Department of Kinesiology, University of Montreal, Montreal, Quebec, Canada. jonathan.tremblay@umontreal.ca
Medicine and Science in Sports and Exercise
|December 19, 2009
Summary
Women show a greater increase in carbohydrate oxidation during exercise with glucose ingestion compared to men, primarily due to a smaller reduction in endogenous carbohydrate use. Oral contraceptive use did not affect fuel selection.
Area of Science:
- Exercise Physiology
- Nutritional Biochemistry
- Sports Science
Background:
- Carbohydrate availability is crucial for endurance exercise performance.
- Understanding sex-based differences in fuel utilization during exercise is important for optimizing nutrition strategies.
- The impact of oral contraceptives on substrate metabolism during exercise requires further investigation.
Purpose of the Study:
- To compare the effects of a high-carbohydrate (CHO) diet and glucose ingestion on fuel selection during prolonged exercise in men and women.
- To investigate potential differences in fuel utilization between women using (W+OC) and not using (W-OC) oral contraceptives.
- To determine the influence of sex on the response to CHO interventions during exercise.
Main Methods:
- Indirect respiratory calorimetry and a 13C-glucose tracer technique were employed to measure substrate oxidation.
- Participants completed a 120-minute exercise bout at 57% VO2max under various dietary and ingestion conditions.
- Exogenous and endogenous carbohydrate oxidation rates were calculated to assess fuel selection.
Main Results:
- In a control condition, men exhibited higher carbohydrate oxidation (% energy yield) than women (62% vs. 53%).
- Both high-CHO diet and glucose ingestion increased carbohydrate oxidation in both sexes, eliminating the initial sex difference.
- Women demonstrated a significantly larger increase in total carbohydrate oxidation with glucose ingestion, particularly due to a smaller decrease in endogenous carbohydrate use, compared to men.
Conclusions:
- A high-CHO diet similarly increased total carbohydrate oxidation in men and women.
- Glucose ingestion during exercise, alone or with a high-CHO diet, had a more pronounced effect on increasing carbohydrate oxidation in women.
- The enhanced response in women was primarily attributed to a preserved rate of endogenous carbohydrate oxidation, rather than increased exogenous glucose utilization.
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