Influence of weight reduction on muscle performance and bone mass, structure and metabolism in obese premenopausal women.

Muscle performance, body composition and bone mass at the lumbar spine and proximal femur with DXA, structural traits at the tibia and radius with pQCT, and biomarkers of bone metabolism were assessed at baseline and after a three-month weight reduction in obese premenopausal women. Associations between changes in weight loss and bone traits were analyzed by linear regression analysis. The mean (SD) weight loss was 4.3 (4.5) kg ranging from 14.8 kg loss to 2.1 kg gain. Muscle performance was well maintained, while no signs of bone loss or structural deterioration were observed. Changes in bone resorption were significantly associated with weight change (for CTX, r=-0.34; p=0.043, and for TRACP5b, r=-0.35; p=0.032). There were borderline (p<0.1) negative correlations between changes in biomarkers and bone traits. Reduced fat mass was associated with slight mean increase in cortical density of the radial shaft. Also total body BMC increased slightly. Changes in both fat and lean mass were associated with a change in BMC. Our findings suggest that mild-to-moderate weight reduction modulated bone turnover slightly, but they do not support the common notion that such a weight reduction would compromise bone rigidity, possibly partly due to well maintained muscle performance.