RESTING METABOLIC-RATE IN OBESE, PREMENOPAUSAL BLACK-WOMEN

In the United States, obesity is more prevalent in black than in non-H ispanic white women. Because low resting metabolic rate (RMR) has been suggested as a risk factor for weight gain, we compared RMR in 22 bla ck and 20 white obese [body mass index (BMI; in kg/m(2)) range: 28.9-4 8.6 and 26.9-44.1, respectively], weight-stable, premenopausal, nondia betic women. RMR was measured on two or three different occasions with in a l-wk period. The black and white groups did not differ significan tly in age, degree of fitness, BMI, fat mass, or fat-free mass (FFM). In each,group, RMR was predicted independently by FFM but not by age, degree of fitness, body fat mass, or body fat distribution. The slopes of the equations predicting RMR from FFM in black and white groups we re not significantly different. However, the black women had significa ntly lower RMRs than the white women after adjustment for FFM measured by five body-composition models: dual-photon X-ray absorptiometry (DX A), hydrodensitometry, total body water, a three-compartment model, a four-compartment model, as well as for the absolute total-body potassi um content as a measure of metabolically active FFM. By each analysis, the black women had significantly lower (P < 0.01) FFM-adjusted RMR t han the white women; this difference ranged from 671 to 889 kJ/d depen ding on the body-composition method used to estimate FFM. This could c ontribute to the difference in the prevalence of obesity in the popula tions represented by these groups.