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 restriction only, or combined weight loss/sodium restriction. INTERVENTION: All TONE participants in the treatment groups attended regular dietary intervention sessions to lose weight, reduce sodium intake, or both that they might refrain from using antihypertensive medications for a period of 15 to 36 months (median = 29 months). MEASUREMENTS: Bone mineral density (BMD) assessed by dual energy X-ray absorptiometry (DXA), serum and urine markers of bone metabolism, and other demographic and clinical data were collected at baseline, 6 months, and 12 months. RESULTS: Women assigned to the weight loss interventions lost 9.2 +/- 1.2 lbs (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 assigned 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 assignment, and other baseline covariates. Regression analyses indicated that total 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 associated with modest decrease in total body BMD. Clinicians recommending weight loss for older postmenopausal women may need to include recommendations for reducing the risk of bone loss.