Ethnic body composition differences: Relationship to human resting energy requirements

There is a growing consensus that resting energy expenditure (REE) differs between African American (AA) and Caucasian (C) women even after adjusting for body mass and composition. The underlying mechanism of this effect remains uncertain, but one hypothesis is that AA and C differ in tissue-organ distribution with a higher proportion of low metabolic rate tissues in AA. We tested this hypothesis by measuring the mass of 4 major heat producing compartments (adipose tissue [AT], skeletal muscle [SM], bone, and residual mass with whole-body MRI and DXA in 22 pairs of wt, ht, and age-matched AA and C women. REE was measured (REEm) by indirect calorimetry and calculated (REEc) from the 4 components from their mass and assumed specific metabolic rates (MR). AT, SM, and bone are low MR components and RM a high MR component. AA had more SM (X plus or minus SD, 1.52 plus or minus 2.48 kg, p