Association between fat mass and bone mineral density among Brazilian women differs by menopausal status: The Pró-Saúde Study

Abstract

Objective: The aim of this study was to investigate the association between bone mineral density (BMD) and fat mass (FM) in a multiethnic population of Brazilian women and to evaluate the influence of total body mass and lean mass on this association.

Methods: This was a cross-sectional study nested within the Pro-Saúde Study, a prospective cohort of university civil servants in Rio de Janeiro. Participants were pre- (n = 100) and postmenopausal (n = 166) women. Total fat, lean mass, and BMD of total body, lumbar spine, and femoral neck were measured using dual energy x-ray absorptiometry. The association of BMD with FM was investigated after adjustment for total body mass (model 1) and lean mass (model 2) and potential confounding variables using multivariate linear regression models.

Results: In model 1, FM was inversely associated with BMD for total body (B = -0.010; P < 0.01) and for femoral neck (B = -0.009 P < 0.05) in premenopausal women. No association between FM and BMD was observed in postmenopausal women. Model 2 yielded direct associations between FM and BMD (total and specific sites; B = 0.003-0.008; P < 0.01) in postmenopausal women only.

Conclusions: Independently of the adjustment used, the results of the present study suggest the absence of an inverse association between FM and BMD in postmenopausal women. Additionally, when adjusted for lean mass, a direct association between FM and bone mass can be observed, suggesting that for postmenopausal women being slightly obese does not confer excessive risk for bone loss and may even result in a bone density advantage.

Keywords: Bone mineral density; DXA; Fat mass; Lean mass; Regression models.