Effect of exercise intensity on 24-h energy expenditure and nutrient oxidation.
Level 2 - randomized trial
Individual randomized crossover trial
PubMed 11842038 · doi:10.1152/japplphysiol.00706.2001
What was done
Sixteen adults (8 men and 8 women) were evaluated on three separate occasions using whole-room indirect calorimetry: a sedentary control day, a low-intensity exercise day (400 kcal at 40% of maximal oxygen consumption), and a high-intensity exercise day (400 kcal at 70% of maximal oxygen consumption). The study measured 24-hour energy expenditure, nutrient oxidation (carbohydrate and fat), and muscle enzymatic profiles.
What was found
Both 24-hour energy expenditure and carbohydrate oxidation were significantly higher on the two exercise days compared to the sedentary control day (Control < Low-intensity = High-intensity), with no difference between exercise intensities. Twenty-four-hour fat oxidation did not differ across the three conditions. Muscle enzymatic profile was not consistently related to 24-hour fat or carbohydrate oxidation. Women had slightly higher rates of 24-hour fat oxidation adjusted for fat-free mass (mg · kg FFM⁻¹ · min⁻¹) and an enzymatic profile favoring fat oxidation compared to men. Specific numerical values for energy expenditure and substrate oxidation rates were not reported in the abstract.
Why it matters
This study shows that when energy expenditure during exercise is matched, the intensity of the exercise does not affect total 24-hour energy expenditure or daily macronutrient oxidation.
Limits
The sample size was small (16 adults). The abstract reports directional findings and statistical equivalence without exact numerical values, effect sizes, or variance estimates. The study assessed acute 24-hour periods in a metabolic chamber, which does not address long-term adaptations to exercise intensity in free-living conditions.
Cited by
- supports Acute fat oxidation during or immediately after exercise does not meaningfully offset 24-hour total energy metabolism to produce greater long-term body fat loss.