Body fat is differentially related to body mass index in U.S.-born African-American and East African immigrant girls

Objective: To examine ethnic differences in adiposity at a given body mass index (BMI) in a sample of U.S.-born African-American and East African immigrant adolescent girls. Methods: In a sample of black adolescent girls (n = 79; ages 14–20) we compared measures of adiposity across the range of BMI-for-age among 55 U.S.-born African-American (mean BMI: 30.4; age: 15.4) and 24 East African immigrant girls (mean BMI: 21.8; age: 16.7). Fat and fat-free mass were assessed with dual-energy X-ray absorptiometry (DXA). We used spline regression to examine the distributions of fat mass index and percent body fat across the range of BMI-for-age z-scores. Results: Compared with African-American girls, East African girls were smaller on all body measures, but appeared to have higher fat mass index and percent body fat at the same BMI-for-age. Conclusions: Our findings indicate that at a given BMI East African immigrants may have greater adiposity than African-American girls. If corroborated in larger samples, our data suggest that the cardiometabolic risks attendant to elevated adiposity may affect East African girls at a lower BMI than in African-American girls. Am. J. Hum. Biol., 2011. © 2011 Wiley-Liss, Inc.