The effects of weight loss induced by hypocaloric diet (HD) alone or combined with aerobic exercise (AEX + HD) on body composition were compared in 61 sedentary obese men aged 60.6 ± 1.0 years (mean ± SEM). Twenty-three subjects in the AEX + HD intervention and 28 subjects in the HD intervention lost a similar amount of body weight (range, 3 to 22 kg). Fifteen men underwent no intervention and served as controls (CON). All groups were of similar body composition at baseline. The HD group decreased caloric intake for 10 months, whereas the AEX + HD group combined HD with AEX (3 times per week) for 10 months. The HD and AEX + HD groups had significant and comparable reductions in body weight (9.3 ± 0.8 v 8.1 ± 0.6 kg), fat mass (6.8 ± 0.5 v 6.7 ± 0.5 kg), and fat-free mass (2.1 ± 0.3 v 1.3 ± 0.3 kg; all P < .05). None of the variables changed significantly in the CON group. Regression lines depicting the relationship between the loss in fat-free mass and the decrease in body weight did not differ significantly in either slope or intercept between the treatment groups. These results suggest that in older obese men, hypocaloric dieting combined with AEX training does not attenuate the loss in fat-free mass that occurs during weight loss by hypocaloric dieting alone.