[The relationship between body composition measured with bioelectric impedance analysis and bone mass in female]

To investigate the effect of fat mass and fat-free mass on bone mineral density (BMD) in pre- and postmenopausal women.

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.

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).

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.