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Does prior acute exercise affect postexercise substrate oxidation in response to a high carbohydrate meal?
Wiley Long1, Katherine Wells, Virginia Englert
1Department of Food Science and Human Nutrition, and Department of Health and Exercise Science, Colorado State University, Fort Collins, CO 80523, USA. christopher.melby@colostate.edu.
Nutrition & Metabolism
|January 29, 2008
Summary
Prior exercise elevates non-esterified fatty acids (NEFA), but a subsequent carbohydrate-rich meal rapidly lowers NEFA. This meal does not alter postprandial fat oxidation compared to resting conditions.
Area of Science:
- Exercise Physiology
- Nutritional Metabolism
- Human Metabolism
Background:
- Mixed meal consumption enhances carbohydrate use and reduces fat oxidation post-meal.
- Endurance exercise boosts fat oxidation and lowers carbohydrate use during recovery.
- Elevated post-exercise non-esterified fatty acids (NEFA) may impact carbohydrate's effect on lipid oxidation.
Purpose of the Study:
- To investigate if prior exercise affects the meal-induced reduction in lipid oxidation.
- To determine the impact of exercise on postprandial substrate utilization.
Main Methods:
- Six healthy adults underwent three randomized trials: exercise followed by carbohydrate meal (Ex/CHO), exercise followed by placebo (Ex/Placebo), and rest followed by carbohydrate meal (NoEx/CHO).
- Blood samples measured plasma glucose, insulin, and NEFA.
- Respiratory gas exchange quantified fat and carbohydrate oxidation rates.
Main Results:
- Post-exercise NEFA levels were double those of the no-exercise condition but rapidly decreased within 2 hours.
- Meal consumption increased insulin and glucose in both Ex/CHO and NoEx/CHO trials.
- Despite higher NEFA post-exercise, carbohydrate and fat oxidation rates did not differ between Ex/CHO and NoEx/CHO conditions.
Conclusions:
- While exercise increases post-exercise NEFA and fat oxidation without a meal, a subsequent meal rapidly reduces NEFA.
- Consuming a meal post-exercise does not lead to higher fat oxidation compared to a non-exercise, post-meal state.
- The metabolic effects of a carbohydrate-rich meal on substrate oxidation are similar whether consumed after exercise or at rest.
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