Resting metabolic rate in african american women

Since in the U.S. obesity is more prevalent in African American (B) than in Caucasian (W) women, we examined differences in the RMR in these two groups. 19 w and 21 B obese, weight stable (BMI range 28-49), premenopauaal (age range 26-49), healthy, nondiabetic, sedentary women, had RMR measured by indirect calorimetry 3 times within a 2 week period. Fat free mass (FFM) vas measured by DEXA, by hydrodensitometry (UWW), by a four compartment model (4C, correcting for total body water and total body bone mineral) and by TBK counting. Aerobic fitness was measured by a submaxima] exercise test and body fat distribution by magnetic resonance imaging. The B and W women were not different with regard to age ( 36±1 vs 34±1 y), VO,max ( 20±1 vs 21±1 ml/Kg/min), BMI (35±1 vs 35±1), fat mass (FM, 43±2 vs 44±2 Kg, by DEXA), FFM (52±2 vs 50±2 Kg, by DEXA) and visceral fat area (110±11 vs 121±13 cm²) . For each group, the RMR (mean of the 3 measured values) was predicted by FFM (by DEXA, r = 0.74, p < 0.1×10^-6 for B women and r = 0.78, p < 0.1×10^-6 for w women) and not by age, vo₂max, FM or body fat distribution variables. The slopes of the prediction equations were parallel for the two groups. After adjusting for FFM, the B women had significantly lower RMR than the W women (-125 Kcal/24 hr. , p < 0.005 by ANCOVA) . The same analysis, adjusting for FFM calculated from 3 other body composition methods ; FFM by UWW, FFM by 4C and using absolute TBK content (in mEq) as a surrogate for active FFM each showed the B women having significantly lower RMR than the W women. The lower RMR adjusted for FFM in B as compared to W women may partly explain the higher prevalence of obesity in the former over the latter.