The contributions of lean tissue mass and fat mass to bone geometric adaptation at the femoral neck in Chinese overweight adults.

Background: Overweight or obese populations may have lower risk of osteoporotic fractures and higher bone mineral density (BMD), while bone strength is determined not only by bone material but also by bone structural parameters. Thus, the influence of body weight on bone geometry was examined in Chinese overweight adults.
Aim: The purpose of this study was to explore how total body lean mass (TBLM) and total body fat mass (TBFM) contribute to the variation of bone geometry at the femoral neck in Chinese overweight adults.
Subjects and Methods: Bone geometric parameters including section modulus (Z), cross-sectional area (CSA), subperiosteal width (W), cortical thickness (CT) and buckling ratio (BR) were compared in 100 overweight (body mass index, BMI >/= 23) vs. 100 underweight subjects (BMI </= 18.5) in Chinese female and male adults aged 20-44 years by multiple regression analyses.
Results: Multiple regression analysis revealed that both TBLM and TBFM were significantly higher in overweight subjects than in underweight subjects. Meanwhile, significant differences in bone geometric parameters (except W) were also detected between the overweight and underweight groups after adjustment for age and height in both sexes (p </= 0.001). Bone bending strength Z and axial strength CSA were 14% and 13% higher in females, as well as 18% and 20% higher in males in the overweight group than in the underweight group, respectively. The significant differences mentioned above were not observed when adjusted for TBLM, age, and height. TBLM seemed to be the strongest significant positive predictor of bone geometric parameters (p < 0.001), with the exception of W in both sexes and BR in females, while TBFM did not contribute significantly to the bone geometric parameters (p > 0.055 for both sexes).
Conclusion: Bone geometry may adapt primarily to mechanical load as represented by TBLM, but TBFM seemed to have no independent effect on bone geometry in Chinese overweight subjects.