Estimation of body fat from anthropometry and bioelectrical impedance in Native American children

OBJECTIVE: Obesity, as measured by body mass index, is highly prevalent in Native American children, yet there are no valid equations to estimate tota l body fatness for this population. This study was designed to develop equa tions to estimate percentage body fat from anthropometry and bioelectrical impedance as a critical part of Pathways, a multisite study of primary prev ention of obesity in Native American children. DESIGN: Percentage fat was estimated from deuterium oxide dilution in 98 Na tive American children (Pima/Maricopa, Tohono O'odham and White Mountain Ap ache tribes) between 8 and 11 y of age. The mean fat content (38.4% +/- 8.1 %) was calculated assuming the water content of the fat-free body was 76%. Initial independent variables were height, weight, waist circumference, six skinfolds and whole-body resistance and reactance from bioelectrical imped ance (BIA). RESULTS: Using all-possible-subsets regressions with the Mallows C (p) crit erion, and with age and sex included in each regression model, waist circum ference, calf and biceps skinfolds contributed least to the multiple regres sion analysis. The combination of weight, two skinfolds (any two out of the four best: triceps, suprailiac, subscapular and abdomen) and bioelectrical impedance variables provided excellent predictability. Equations without B IA variables yielded r(2) almost as high as those with BIA variables. The r ecommended equation predicts percentage fat with a root mean square error = 3.2% fat and an adjusted r(2) = 0.840. CONCLUSION: The combination of anthropometry and BIA variables can be used to estimate total body fat in field studies of Native American children. Th e derived equation yields considerably higher percentage fat values than ot her skinfold equations in children.