Racial/ethnic differences in body fatness among children and adolescents.

Although the BMI is widely used as a measure of adiposity, it is a measure of excess weight, and its association with body fatness may differ across racial or ethnic groups. To determine whether differences in body fatness between white, black, Hispanic, and Asian children vary by BMI-for-age, and whether the accuracy of overweight (BMI-for-age>or=Centers for Disease Control and Prevention (CDC) 95th percentile) as an indicator of excess adiposity varies by race/ethnicity. Total body dual-energy X-ray absorptiometry (DXA) provided estimates of %body fat among 1,104 healthy 5- to 18-year-olds. At equivalent levels of BMI-for-age, black children had less (mean, 3%) body fatness than white children, and Asian girls had slightly higher (1%) levels of %body fat than white girls. These differences, however, varied by BMI-for-age, with the excess body fatness of Asians evident only among relatively thin children. The ability of overweight to identify girls with excess body fatness also varied by race/ethnicity. Of the girls with excess body fatness, 89% (24/27) of black girls, but only 50% (8/16) of Asian girls, were overweight (P=0.03). Furthermore, the proportion of overweight girls who had excess body fatness varied from 62% (8/13) among Asians to 100% (13/13) among whites. There are racial or ethnic differences in body fatness among children, but these differences vary by BMI-for-age. If race/ethnicity differences in body fatness among adults also vary by BMI, it may be difficult to develop race-specific BMI cut points to identify equivalent levels of %body fat.