Body fat, lean mass and bone density of the spine and forearm in women

The aim of this study was to determine the relative contributions of fat mass and lean mass to the variability of bone mineral density (BMD) of the lumbar spine and proximal 1/3 forearm in Bulgarian women. 180 women aged 21 through 76 years participated (mean age 50.8 +/- 9.7 years). 130 of them were postmenopausal. Lumbar spine and forearm BMD were measured by dual-energy X-ray absorptiometry, followed by a whole-body scan for body composition examination (Hologic QDR 4500 A device, software version 1.26). The strongest linear correlation was found with body weight (r2=0.231, p < 0.001). Using this model, 18.1 % of the variability of lumbar spine BMD was attributable to fat mass and 16.0 % to lean mass. The relative influence of fat mass on L1-L4 BMD was greater than that of lean mass (standardized regression coefficient 0.291 versus 0.199). There were weak correlations of body weight, fat and lean mass with the forearm BMD. Lean mass correlated slightly better (r=0.187, p=0.050) to forearm BMD than fat mass (r=0.162, p=0.055). In conclusion, the differentiation between fat and lean mass does not strengthen the BMD correlations beyond that with total body weight.