Elevated Lipid Oxidation in Men Following Endurance Exercise

Abstract

Exercise increases metabolic rate and the exercise-induced perturbation in metabolism persists into recovery. PURPOSE: We sought to confirm findings of elevated lipid oxidation in postabsorptive men for 3 hr following 60–90 min of exercise (day 1) and to test the hypothesis that lipid oxidation would remain elevated above that in the resting control trial on the following morning (day 2). METHODS: Ten men were studied by indirect calorimetry on 2 different occasions during and for 3 hr after isoenergetic exercise bouts [∼90 min at 45% VO2peak (Mod) and ∼60 min at 65% VO2peak (Hard)], and on a third occasion to obtain time of day-matched resting control (Con) data. Subjects rested the day prior to day 1 and received a standardized diet to cover energy needs (IOM, 2002). On day 1 of each trial, participants received individualized diets with the same energy content and macronutrient composition (breakfast 3 hr before exercise; lunch 3 hr after exercise, followed by a dinner and snack that evening). On the morning of day two, participants were transported to the laboratory overnight fasted for an indirect calorimetry measurement. RESULTS: Exercise energy expenditure was elevated above resting by 693 +/− 40 kcal in Mod and 704 +/− 42 kcal in Hard with no significant difference between Mod and Hard. We confirm previous findings of elevated lipid oxidation for 3 hr of postabsorptive rest following 60–90 min of isoenergetic exercise with no difference between Mod and Hard. As well, on the morning of day 2, following both Mod and Hard exercise trials, lipid oxidation remained elevated above Con (P < 0.05) with no significant difference between exercise intensities (0.38 +/− 0.08, 0.56 +/− 0.05, and 0.50 +/− 0.04 kcal/min in Con, Mod, and Hard, respectively). CONCLUSION: Compared to a sedentary control, lipid oxidation remains elevated for at least 20 hr after an endurance exercise bout when energy intake is held constant. Supported by NIH grant AR 42906 to GAB.