Comparison of risk factors for obesity in young, nonobese African-Americanand Caucasian women

OBJECTIVE: To determine whether specific risk factors for obesity were more evident in young, normal-weight African-American (AA) compared to Caucasia n-American (CA) women. DESIGN: Cross-sectional age-matched study. SUBJECTS: Young, nonobese, sedentary AA (n = 13, 22.5 y of age, 23.6% body fat) and CA women (n = 11, 21.5 y of age, 24.0% body fat). MEASUREMENTS: Aerobic physical fitness (peak VO2), resting metabolic rate ( RMR), resting and submaximal exercise fat oxidation rates, total daily ener gy expenditure (TDEE) by the doubly-labeled water method, physical activity energy expenditure (PAEE), skeletal muscle glycolytic (phosphofructokinase activity (PFK)) and beta -oxidative (beta -hydroxy-acyl CoA dehydrogenase (beta -HADH)) activity, and insulin sensitivity estimated by the insulin-au gmented frequently sampled intravenous glucose tolerance test. RESULTS: The AA and CA subjects were similar in age, body mass index and bo dy composition, but the AA women exhibited lower peak VO2. There were no gr oup differences in RMR adjusted for body composition, or in the rates of su bmaximal exercise energy expenditure or fat oxidation, and no difference in skeletal muscle beta -HADH or PFK activity. The AA women exhibited lower i nsulin sensitivity and greater acute insulin response to glucose. The mean TDEE for the AA women was only 74% that of the CA women, primarily due to a lower physical activity energy expenditure (AA group: x PAEE = 1246 +/- 43 8 kJ/day; CA group: x = 3310 +/- 466 kJ/day. CONCLUSION: These data indicate that PAEE and its correlates of peak aerobi c capacity and insulin sensitivity are lower in young, nonobese AA women co mpared to their CA counterparts.