Background: Studies of weight loss and changes in bone mineral density (BMD) have primarily been short-term trials in obese subjects.

Objective: We examined the effects of a 5-year intervention designed to prevent menopausal weight gain or promote modest weight loss on BMD in premenopausal women participating in the Women's Healthy Lifestyle Project (WHLP).

Design: We enrolled 373 premenopausal women (age 44-50 yr) and randomly assigned them to either lifestyle intervention (175 women, low fat dietary modification, weight loss, and physical activity intervention) or control group (198 women). BMD and body weight were measured at baseline, annual follow up visits (18, 30, 42, 54 months), and two post intervention follow-ups (66, 78 months). BMD was measured by dual x-ray absorptiometry.

Results: Over the 54 months of intervention, women in the intervention group lost 0.4 kg, while control women gained 2.6 kg (p=0.011). The intervention group experienced significantly greater hip bone loss (-0.20%/yr) than the control group (-0.03%/yr). During the post intervention, differences in rates of bone loss disappeared. When considering both menopausal status and use of hormone therapy (HT), the annualized BMD changes were lower in women reporting HT use; nevertheless, among women on HT, those who lost > 3% body weight experienced greater total hip BMD loss (-0.25%/yr) compared to those who gained weight (-0.02%/yr)(p=0.025).

Conclusions: Women randomized to a lifestyle intervention aimed at preventing menopausal weight gain or promoting modest weight loss experienced greater rates of hip bone loss than control women.