Association between bone mineral density, lean mass, and fat mass among healthy middle-aged premenopausal women: a cross-sectional study in southern Sri Lanka

Associations between lean mass, fat mass, and bone mass have been reported earlier; however, most of those studies have been done in Caucasian populations, and data from Asian countries, especially those in South Asia, are limited. We examined the associations between lean mass, fat mass, bone mineral density (BMD), and bone mineral content (BMC), determined by dual-energy X-ray absorptiometry technology, in a group of healthy, middle-aged, premenopausal female volunteers. The mean (SD) age of the women (n = 106) was 42.1 (6.1) years and the mean (SD) body mass index was 24.3 (3.6) kg/m². Total body BMD, total body BMC, and BMD in total spine, total hip, and femoral neck showed statistically significant partial correlations (adjusted for age) with total fat mass (r = 0.19–0.43, P < 0.05) and lean body mass (r = 0.28–0.54, P < 0.05). Truncal fat mass correlated positively with total body BMC and BMD at total hip and femoral neck (r = 0.33–0.40, P < 0.001). When a stepwise regression model was fitted, lean mass remained the strongest predictor of total body BMD, total body BMC, and total spine BMD (regression coefficients = 0.004–0.008 g/cm² per 1-kg change in lean mass, P < 0.001). Similarly, crude BMD and BMC increased across the tertiles of lean mass (P trend < 0.05). We show that lean mass is the strongest predictor of total body BMC and BMD at different sites, although positive correlations with fat mass also exist.