Association Between Lean Mass, Fat Mass, and Bone Mineral Density: A Meta-analysis

Body weight is the most important anthropometric determinant of bone mineral density (BMD). Body weight is mainly made up of lean mass (LM) and fat mass (FM), and which component is more important to BMD has been a controversial issue. This study sought to compare the magnitude of association between LM, FM, and BMD by using a meta-analytic approach. Using an electronic and manual search, we identified 44 studies that had examined the correlation between LM, FM, and BMD between 1989 and 2013. These studies involved 20 226 men and women (4966 men and 15 260 women) aged between 18 and 92 years. We extracted the correlations between LM, FM, and BMD at the lumbar spine, femoral neck, and whole body. The synthesis of correlation coefficients was done by the random-effects meta-analysis model. The overall correlation between LM and femoral neck BMD (FNBMD) was 0.39 (95% confidence interval, 0.34 to 0.43), which was significantly higher than the correlation between FM and FNBMD (0.28; 95% confidence interval, 0.22 to 0.33). The effect of LM on FNBMD in men (r = 0.43) was greater than that in women (r = 0.38). In premenopausal women, the effect of LM on BMD was greater than the effect of FM (r = 0.45 vs r = 0.30); however, in postmenopausal women, the effects of LM and FM on BMD were comparable (r = 0.33 vs r = 0.31). LM exerts a greater effect on BMD than FM in men and women combined. This finding underlines the concept that physical activity is an important component in the prevention of bone loss and osteoporosis in the population.