Whole body bone, fat, and lean mass in black and white men

This research describes the effects of age, ethnicity, and body size and composition on whole body bone mass and bone density in healthy black and white men. We measured 79 male subjects, 42 white and 37 black, ranging in age from 33 to 64 years. Whole body bone mineral content (WBBMC) and bone mineral density (WBBMD), as well as fat and lean mass, were evaluated with a Hologic 1000W bone densitometer. We explore the utility of different methods of controlling for variations in body size in the two ethnic groups. There are statistically significant ethnic differences only in the bone mass variables. The black men had a 15% higher WBBMC (3111 vs. 2712 g, p < 0.0001) and a 8% higher WBBMD (1.25 vs. 1.16 g/cm2, p = 0.001) than the white men. Dividing WBBMD by height reduced the black/white difference to 6%. WBBMC, WBBMC/height, and WBBMD are strongly and significantly correlated with weight, body mass index (BMI), and body composition; correlations tended to be lower for WBBMD/height. Age is not significantly correlated with any of the variables in either ethnic group (p > or = 0.10). In multivariate linear regression models for predicting WBBMC or WBBMD, the two best models contained height, weight, and an interaction of ethnicity and weight (model r2 = 0.72 for WBBMC and r2 = 0.47 for WBBMD); and height, lean mass, and an ethnicity-fat interaction (model r2 = 0.69 for WBBMC and r2 = 0.46 for WBBMD). Using analysis of covariance, we found that controlling for lean mass and height reduced the black/white difference in bone mass from 14.7 to 9.8%.