This study examined whether exercise training facilitates maintenance of body weight at reduced levels following weight loss by attenuating weight loss-induced reductions in resting metabolism and fat oxidation. The effects of 12 weeks (three times per week) of either aerobic or weight training exercise on body weight, body composition, and energy metabolism during rest and following a meal in 18 older (mean +/- SE, 61 +/- 1 years; range, 56 to 70) subjects who had recently lost a mean of 9 +/- 1 kg were studied. During the exercise training period, the aerobic training group (five women, four men) had a significant (P < .05) reduction in body weight (-2.5 +/- 0.6 kg) as compared with the weight training group (five women, four men) (0.4 +/- 0.9 kg). Eight of nine aerobic training subjects lost additional weight, while six of nine weight training subjects gained weight. Neither type of training reversed the depressions in resting metabolism or fat oxidation rates (ie, resting or postprandial) that had occurred as a consequence of the prior weight loss. Thus, alterations in resting metabolism or fat oxidation (resting or postprandial) do not appear to be the mechanism(s) by which exercise training facilitates maintenance of diet-induced weight loss.