Body composition predicts bone mineral density and balance in premenopausal women

Low bone mineral density (BMD) and poor stability both contribute to increa sed risk of fractures associated with a fall. Our aim in this cross-section al study was to determine the anthropometric and/or performance variables t hat best predicted BMD and stability in women. BMD, body composition, muscl e strength, muscle power, and dynamic stability were evaluated in 61 women (age 40 +/- 4 years; % body fat 27% +/- 5%). In correlation analyses, BMD a t all sites was significantly related to height, lean mass, strength, and l eg power (r(2) = 0.25-0.49). Significant inverse relationships were found b etween all independent variables and dynamic stability (r(2) = 0.23-0.52). In stepwise regression, lean mass independently predicted BMD at the femora l neck (R-2 = 0.20), total hip (R-2 = 0.24), and whole body (R-2 = 0.17), w hereas hip abductor torque predicted 23% of the variance in trochanter BMD and added 6% to the variance in total hip BMD. Leg power was the only predi ctor of spine BMD (R-2 = 0.14). Fat and lean mass both independently predic ted poor performance on postural stability, with fat mass contributing 31% of the total variance (R-2 = 0.38). In conclusion, we found lean mass to be a robust predictor of BMD in premenopausal women. Furthermore, both hip ab ductor torque and leg power independently predicted BMD at clinically relev ant fracture sites (hip and spine). The finding that higher fat mass contri butes to the majority of the variance in poor stability indicates that grea ter fat mass may compromise stability and, thus, increase fall risk in heav ier individuals.