Effect of voluntary weight loss on bone mineral density in older overweight women

OBJECTIVES: To examine the effect of diet and exercise-induced weight loss on bone mineral density in overweight postmenopausal women. DESIGN: A I-year prospective, randomized clinical trial. SETTING: Two university medical school research centers. PARTICIPANTS: Sixty-seven overweight postmenopausal women, a subset of the women who participated in the Trial of Nonpharmacological Interventions in the Elderly (TONE) to control hypertension. The participants were assigned randomly to one of four groups: usual care, weight loss only, sodium restri ction only, or combined weight loss/sodium restriction. INTERVENTION: All TONE participants in the treatment groups attended regula r dietary intervention sessions to lose weight, reduce sodium intake, or bo th that they might refrain from using antihypertensive medications for a pe riod of 15 to 36 months (median = 29 months). MEASUREMENTS: Bone mineral density (BMD) assessed by dual energy X-ray abso rptiometry (DXA), serum and urine markers of bone metabolism, and other dem ographic and clinical data were collected at baseline, 6 months, and 12 mon ths. RESULTS: Women assigned to the weight loss interventions lost 9.2 +/- 1.2 l bs (mean +/- SE) at 6 months and 7.7 +/- 2.0 lbs at 12 months compared with 1.8 +- 1.0 Ibs at 6 months and 1.9 +/- 1,6 Ibs at 12 months for those assi gned to no weight loss intervention (P <.0001). Weight loss was correlated with a decrease in total body BMD (P =.004) and an increase in osteocalcin (P =.004) after controlling for baseline bone measures, intervention assign ment, and other baseline covariates. Regression analyses indicated that tot al body BMD decreased by 6.25 +/- 2.06 g/cm(2) x 10(-4) for each pound of - weight loss. CONCLUSIONS: Voluntary weight loss in overweight postmenopausal women is as sociated with modest decrease in total body BMD. Clinicians recommending we ight loss for older postmenopausal women may need to include recommendation s for reducing the risk of bone loss.