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

Abstract:

OBJECTIVE: To determine whether specific risk factors for obesity were more evident in young, normal-weight African-American (AA) compared to Caucasian-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 VO<inf>2</inf>), resting metabolic rate (RMR), resting and submaximal exercise fat oxidation rates, total daily energy expenditure (TDEE) by the doubly-labeled water method, physical activity energy expenditure (PAEE), skeletal muscle glycolytic (phosphofructokinase activity (PFK)) and β-oxidative (β-hydroxy-acyl CoA dehydrogenase (β-HADH)) activity, and insulin sensitivity estimated by the insulin-augmented frequently sampled intravenous glucose tolerance test. RESULTS: The AA and CA subjects were similar in age, body mass index and body composition, but the AA women exhibited lower peak VO<inf>2</inf>. There were no group differences in RMR adjusted for body composition, or in the rates of submaximal exercise energy expenditure or fat oxidation, and no difference in skeletal muscle β-HADH or PFK activity. The AA women exhibited lower insulin 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 ± 438 kJ/day; CA group: x= 3310 ± 166 kJ/day. CONCLUSION: These data indicate that PAEE and its correlates of peak aerobic capacity and insulin sensitivity are lower in young, nonobese AA women compared to their CA counterparts.