EXERCISE INCREASES FAT OXIDATION AT REST UNRELATED TO CHANGES IN ENERGY-BALANCE OR LIPOLYSIS

The hypothesis that exercise increases fat oxidation at rest independe ntly of changes in energy balance, body composition, and/or lipolysis was tested in 21 volunteers. After a period of energy balance, volunte ers were randomly allocated to one of four groups: control, overfed (O F), overfed and exercised (OF-EX), and exercised (EX). OF and OF-EX we re overfed 50% excess of energy balance calories; OF-EX and EX spent 5 0% excess of energy balance calories during daily exercise sessions. E xercise increased fat oxidation at rest independently of dietary intak e (OF-EX = +22 +/- 2.4, EX = +23 +/- 1.5 mg/min) and reduced carbohydr ate oxidation (OF-EX = -49 +/- 6.2, EX = -46 +/- 5.4 mg/min). Voluntee rs in the OF group had an increase in carbohydrate oxidation (85 +/- 5 .9 mg/min) and a decline in fat oxidation (-33 +/- 1.4 mg/min). Protei n oxidation did not change in any group. These changes occurred withou t a direct relation with changes in lipolysis and persisted even when expressed as a percentage or as an absolute equivalent of resting meta bolic rate in calories. Thus exercise, independent of changes in energ y intake and body composition and not related to changes in lipolysis, increases fat oxidation at rest, which may explain the beneficial eff ects of exercise in weight loss programs.