Lean mass as a significant determinant of regional and total body bone mineral density in premenopausal women

We investigated the relations of body composition to regional and total body bone mineral density (BMD) in 275 healthy Japanese premenopausal women (mean age, 37.1 ± 9.2 years; range, 16–55 years). In all subjects, the right side was dominant. BMD of the head, bilateral arms, lumbar spine (L2–L4), bilateral legs, and total body were measured using whole-body scanning by dual-energy X-ray absorptiometry (DXA). Total fat mass, total lean mass, regional lean mass, and regional fat mass were measured by DXA. Baseline characteristics including age, height, body weight, and body mass index were recorded for each subject. Possible correlations between regional or total body BMD with variables were determined on univariate and stepwise multiple regression analysis. BMD, lean mass, and fat mass were compared between the bilateral extremities. Total lean mass for the right arm, regional lean mass for the left arm, total lean mass for the lumbar spine, body weight for the bilateral legs, and total lean mass for the whole body were the most significant determinants of BMD on stepwise multiple regression analysis. Right-arm BMD was significantly higher than left-arm BMD. However, no significant difference was observed between BMD in the right and left legs. We concluded that lean mass is a more significant determinant of regional and total body BMD than fat mass in premenopausal women.