Density of lean body mass is greater in blacks than in whites

Abstract

Previous studies have reported that Blacks have 10–20% more bone mineral than Whites of the same height. Theoretically, this should mean that the lean body mass of Blacks is denser than that of Whites, such that formulas for calculating lean body mass from density in Whites will overestimate the lean body mass (and thus underestimate fatness) in Blacks. To determine if the lean body mass of Blacks is indeed denser than that of Whites, we measured density, total body water, and anthropometric dimensions in 19 white and 15 black male college students. The black and white cohorts were nearly identical in height, weight, and total body water. Among the Whites there was no significant difference between the observed density and that predicted from anthropometry, nor were there any significant differences between the dimensions of body composition calculated from total body water and from observed density. Among the Blacks, however, the observed density was significantly greater than that predicted from anthropometry, and the lean body mass calculated from observed density was significantly greater than that calculated from total body water. These results are consistent with the hypothesis that the lean body mass of the Blacks is denser than that of the Whites. Separate formulas should therefore be used for converting density to body composition. Based on our data, the correct formula for Blacks is: %fat = 100 X [(4.374/density) - 3.928]. This formula indicates a lean body density of 1.113 g/cm3 in Blacks compared with 1.100 in Whites.