PURPOSE

To determine whether 16 months of moderate-intensity exercise training changes resting metabolic rate (RMR) and substrate oxidation in overweight young adults.

METHODS

Participants were randomly assigned to nonexercise control (CON, 18 women, 15 men) or exercise (EX, 25 women, 16 men) groups. EX performed supervised and verified exercise 3-5 d/wk, 20-45 min/session, at 60-75% of heart-rate reserve. Body mass and composition, maximal oxygen consumption (VO2max), RMR, and resting substrate oxidation were assessed at baseline and after 9 and 16 months of training.

RESULTS

EX men had significant decreases from baseline to 9 months in body mass (94.6+/-12.4 to 89.2+/-9.5 kg) and percent fat (28.3+/-4.6 to 24.5+/-3.9). CON women had significant increases in body mass (80.2+/-8.1 to 83.2+/-9.2 kg) from baseline to 16 months. VO2max increased significantly from baseline to 9 months in the EX men (3.67+/-0.62 to 4.34+/-0.58 L/min) and EX women (2.53+/-0.32 to 3.03+/-0.42 L/min). RMR increased from baseline to 9 months in EX women (1,583+/-221 to 1,692+/-230 kcal/d) and EX men (1,995+/-184 to 2,025+/-209 kcal/d). There were no significant differences within genders for either EX or CON in fat or carbohydrate oxidation. Fat oxidation was significantly higher for women than for men at 9 months in both CON and EX groups.

CONCLUSIONS

Regular moderate-intensity exercise in healthy, previously sedentary overweight and obese adults increases RMR but does not alter resting substrate oxidation. Women tend to have higher RMR and greater fat oxidation, when expressed per kilogram fat-free mass, than men.