The effect of body composition on bone density in pre- and postmenopausal women

Objectives: To investigate the relative contribution of body composition (lean and fat) to bone mineral density (BMD), 196 premenopausal and 128 postmenopausal Japanese women were enrolled. Methods: Total fat mass, total lean mass, lumbar BMD (L2–L4), and total body BMD were measured by dual-energy X-ray absorptiometry (DEXA, Hologic QDR 2000, MA, USA). Physical characteristics were also recorded for each subject. Correlation between BMD and variables were calculated for each of the two groups in single and stepwise regression analyses. Results: Total lean mass was significantly higher in premenopausal women than postmenopausal women (P < 0.0001), while body weight, body mass index, and total fat mass were not different between the two groups. In stepwise regression analysis, total lean mass was the most powerful determinant of lumbar BMD and total body BMD in premenopausal women. In postmenopausal women, total fat mass was the most significant determinant of lumbar BMD, while total lean mass was the most significant determinant of total body BMD. Conclusions: These findings suggest that there is a difference between pre- and postmenopausal women in the relative contribution of lean and fat mass. Total lean mass is the most significant determinant of BMD in premenopausal women. On the other hand, total fat mass may have some advantages in maintaining BMD in postmenopausal women.