Physical activity in free-living, overweight white and black women: divergent responses by race to diet-induced weight loss

Background: Black women are at greater risk of obesity than are white women, perhaps because of their lower levels of physical activity. Objective: We compared free-living activity energy expenditure (AEE) in sedentary white and black women (in overweight and normal-weight states) and in never-overweight control subjects. Design: Subjects included 46 women (23 white, 23 black) studied while overweight and after reaching a normal weight and 38 female control subjects (23 white, 15 black). Diet, without exercise training, resulted in a mean weight loss of 13 kg and a body mass index (in kg/[m.sup.2]) Results: No significant racial differences in body composition, before or after weight loss, were found. After weight loss, AEE and aerobic capacity increased in the white women and decreased in the black women (P < 0.05 and P < 0.02, respectively). After weight loss, but not before, the white women had a significantly higher mean AEE than did the black women (2448 [+ or -] 979 and 1728 [+ or -] 1373 kJ/d, respectively; P < 0.05), approximating AEEs in the white (2314 [+ or -] 105) and black (2310 [+ or -] 1251) control subjects. Conclusions: Relative to the responses of the white women to diet-induced weight loss, the black women became less fit and less physically active. Induction of a normal body weight in overweight black women appeared to produce a more obesity-prone state, favoring weight relapse. KEY WORDS Overweight, obesity, weight loss, body composition, energy expenditure, energy economy, physical activity, exercise, African American women