Objective: To investigate the effect of fat mass and fat-free mass on bone mineral density (BMD) in pre- and postmenopausal women.
Methods: 282 premenopausal women with regular menstruation and 205 postmenopausal women were enrolled in this study. BMD at lumbar spine (L(2 - 4)) and femoral neck (FN) were measured with dual-energy X-ray absorptiometry (DEXA). Fat mass and fat-free mass were measured with bioelectric impedance analysis (BIA). Height, weight, waist and hip circumference were recorded. Body mass index (BMI) and waist hip ratio (WHR) were calculated.
Results: Fat mass and fat-free mass were significantly positively correlated with L(2 - 4) and FN BMD in both pre- and postmenopausal women (P < 0.01). Multiple regression analysis showed that in premenopausal women, fat-free mass and age were significant determinants of L(2 - 4) BMD (R(2) = 0.077, P = 0.000), while fat-free mass, age and BMI were significant determinants of FN BMD (R(2) = 0.130, P = 0.000). In postmenopausal women, fat mass and age were significant determinants of BMD at L(2 - 4) and FN (R(2) were 0.153 and 0.184 respectively, P = 0.000).
Conclusions: Fat mass and fat-free mass have different effects on BMD in pre- and postmenopausal women. Fat-free mass is a significant determinant of BMD in premenopausal women, while fat mass contributes most to BMD in postmenopausal women.