PURPOSE: To evaluate the effects of physical activity on bone mineral density, bone mineral content, and lean mass in postmenopausal, overweight/obese women. METHODS: We conducted a 12-month randomized controlled aerobic exercise intervention versus control in 173 sedentary, overweight/obese, postmenopausal women, aged 50 to 75 yr. The exercise prescription consisted of >= 45 min of moderate-intensity aerobic exercise (60 to 75% of maximal heart rate), 5 d/wk for 12 months. Control participants attended 45-min stretching sessions once a week. Ninety-eight percent (N = 170) completed the trial. Exercisers averaged 172 min/wk (SD 89) of exercise and expended 3828 kJ/wk (SD 2053). We assessed body fat, total lean mass, and total body bone mineral density and content using dual-energy x-ray absortiometry (DXA). We compared baseline with 12-month changes in exercisers versus controls. RESULTS: Exercisers lost significantly more weight than stretchers (1.3-kg loss versus 0.1-kg gain, p = 0.01). However, no differences between exercisers and controls in the change from baseline to 12 months were detected: exercisers' average bone mineral density increased by 0.005 g/cm and controls' by 0.003 g/cm (p = 0.61). Similarly, no significant differences were detected for bone mineral content. Lean mass increased by 0.2 kg in both groups (p = 0.84). CONCLUSION: Overall, the results from this randomized controlled study suggest that a yearlong moderate-intensity aerobic exercise intervention does not affect total body bone mineral density, bone mineral content, or lean mass in overweight/obese postmenopausal women.

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