Racial Differences in Daily Physical Activity Level and Body Composition in Obese, Postmenopausal Women

Abstract

Survey data show that physical inactivity is more prevalent in blacks than whites, and this may be one of the predisposing factors to the greater incidence of obesity in blacks. PURPOSE: To determine whether there are differences in body composition, resting metabolic rate (RMR) and daily physical activity (PA) in healthy, older, obese black and white women. METHODS: Daily PA (by RT3 activity monitor for 5–7 days), body composition (by dual energy x-ray absorptiometry), RMR, (via indirect calorimetry), and maximal aerobic capacity (VO2max, via treadmill testing) were determined in 49 obese, (BMI=33.14±3.75 kg/m2), postmenopausal (age= 58.0±5.2 yrs) women (n=28 white; n=21 black). RESULTS: White women had a lower BMI (32.0±3.5 vs 34.6±3.7 kg/m2; p=0.016), less fat mass (37.0±6.7vs 41.7±6.0kg; p=0.015), and less lean mass (48.0±4.4vs 52.6±5.2 kg; p=0.002), but had a higher relative VO2max (21.3±2.8 vs 19.1±2.8 ml/kg/ min; p=0.011). Absolute RMR (1296±157 vs 1271±193 kcal/d; p=0.618) did not differ by race, but RMR per kilogram of lean mass was higher in white versus black women (27.1±2.7 vs 24.3±3.6; p=0.003). The average daily PA level was not different between white (571±199 kcal/d) and black (551±129 kcal/d) women (p=0.72). However, correlation analyses suggest racial differences exist in the relationship between and body composition. In whites, PA was directly related to BMI, fat mass and lean mass, while there was no relationship between PA and body composition in blacks. RMR was related to fat mass and lean mass in both white and black women.TableCONCLUSION: In these obese, postmenopausal women, racial differences were seen in body composition despite participation in equal amounts of PA. In addition, PA was related to the amount of fat mass and lean mass in white women, while in blacks there was no relationship between PA and body size. Supported by NIH grants R01-AG/DK20583 and the WFU GCRC (M01-RR07122)