Evaluation of body fat in fatter and leaner 10-y-old African American and white children: the Baton Rouge Children's Study

Background: Only a few published studies in children used several methods t o compare body fat in large groups of fatter and leaner multiethnic childre n. We hypothesized that the preferred methods of determining body fat may d iffer in children with larger compared with smaller amounts of body fat, in boys compared with girls, and in African Americans compared with whites. Objective: Our objective was to evaluate several methods of predicting body fat in 10-12-y-old white and African American boys and girls. Design: The body fat of 129 African American and white boys and girls aged 10-12 y, distributed equally by sex and race, was measured with use of dual -energy X-ray absorptiometry (DXA), underwater weighing (densitomehry), iso tope dilution ((H2O)-O-18), bioelectrical impedance, skinfold thicknesses, corporal diameters, and circumferences. Results: With use of DXA as the criterion variable, body fat was bimodally distributed in the boys and skewed to higher values in the girls. Biceps sk infold thickness had the highest predictive value of any single skinfold th ickness compared with DXA fat. All formulas for estimating body fat from sk infold thicknesses, body density, or impedance performed better in the chil dren in the upper one-half of the fat distribution (the fatter children) th an in those in the lower one-half (the leaner children). Body mass index wa s highly correlated with body fat (R-2 = 0.77); there was a good correlatio n for the fatter children (R-2 = 0.66) and no correlation for the leaner ch ildren (R-2 = 0.09). The hydration of the fat-free mass was significantly h igher in the fatter children than in the leaner ones (79.2% compared with 7 6.7%). Conclusions: These data are consistent with the hypothesis that all methods of estimating body fat work better in children with larger amounts of body fat. The best formulas use skinfold thicknesses, bioelectrical impedance, and a 4-compartment model.