PREDICTORS OF RESTING METABOLIC RATE IN POSTMENOPAUSAL AFRICAN-AMERICAN AND CAUCASIAN WOMEN

Abstract

Increased prevalence of obesity among young African American (AA) women has been attributed to reduced resting metabolic rate (RMR). It is unclear if RMR differs between postmenopausal AA and Caucasian (CA) women and it is also unknown if predictors of RMR are race dependent. PURPOSE To analyse the influence of race on RMR and evaluate if predictors of RMR differ between AA and CA postmenopausal women. METHODS We analysed data from 24 AA (age: 56.3 ± 5.0 yrs) and 23 CA (age: 58.6 ± 6.1 yrs) women. RMR was determined in the morning following a 12 hour fast, using a ventilated hood system. Subjects completed tests of maximal exercise with metabolic measurements, waist to hip ratio and body composition. RESULTS No race differences were found for the BMI (AA, 28.3 ± 6.6 kg/m2; CA, 26.0 ± 4.4 kg/m2), percent of body fat (AA, 39.4 ± 8.0%; CA, 40.1 ± 7.0%) and peak oxygen uptake (AA, 25.0 ± 5.9 mL/kg/min; CA, 27.4 ± 5.3 mL/kg/min). There was no difference in RMR between the races (AA, 1237.7 ± 156.8 kcal/day; CA, 1259.5 ± 197.7 kcal/day) even when adjusting for body mass. However when adjusting for Lean Body Mass (LBM) RMR was lower in AA compared with CA women (p < 0.05). LBM (p < 0.001), body mass (p < 0.001) and peak oxygen uptake (p < 0.05) were related to RMR in AA women but only LBM (p < 0.01) and body mass (p < 0.001) were related with RMR in CA women. Using a stepwise regression only body mass was significantly related on both groups (p < 0.001). CONCLUSION These data show that the RMR predictors differ little between AA and CA women and only body mass was a significant independent predictor of RMR, despite differences in RMR when adjusted for LBM.