Postexercise macronutrient oxidation: A factor dependent on postexercise macronutrient intake

Abstract

Background: It has been widely shown that exercise increases postexercise fat oxidation and energy expenditure. Objective: The aim of this study was to investigate the effect of exercise on postexercise substrate oxidation and energy expenditure when the exercise-induced expenditure of energy and macronutrients oxidized is compensated by an equivalent intake immediately after exercise. Design: Twenty-four-hour energy expenditure (24EE) and macronutrient oxidation of 8 young men were measured in a whole- body indirect calorimeter under the 2 following, randomly assigned conditions: 1) a control session of sedentary activities in the calorimeter for 61 h and 2) a similar session preceded by 60 min of exercise at 50% of maximal oxygen consumption. Immediately after exercising, subjects ingested a milk shake containing the same amount of energy (above resting metabolic rate) expended during exercise and with a food quotient corresponding to the mean exercise respiratory quotient. 24EE and substrate oxidation were compared between conditions on a day-to-day basis (days 1, 2, and 3) and for the 61-h observation period. Results: There was no difference in 24EE between the 2 conditions. Moreover, the composition of the postexercise fuel mix oxidized, as reflected by the respiratory quotient, was strictly the same under the 2 conditions. Conclusion: Voluntary postexercise compensations in energy and macronutrient intakes play a major role in the ability of exercise to alter postexercise substrate utilization.