Assessing the body composition of 6-17-year-old black and white girls in field studies

The purpose of the study was to develop ethnic-specific equations for fat-f ree mass (FFM) from selected anthropometric dimensions and bioelectrical im pedance measures of resistance (R) and reactance (X-c) for use in the NHLBI Growth and Heath Study. Using dual-energy X-ray absorptiometry measures of body composition as the dependent variable and field measures of body comp osition by anthropometry and bioelectrical impedance as the explanatory var iables, ethnic-specific prediction equations were developed on a sample of girls representing a wide range of ages and BMI. The equations were cross-v alidated using (1) the Prediction of Sum of Squares (PRESS) statistic and ( 2) an independent sample of 20 girls of each race from a study conducted at the National Institute of Child Health and Human Development (NICHD). Subj ects were 65 White and 61 Black girls 6-17 years of age. The best race-spec ific equations for FFM each explained 99% and 97% of the variance in the Wh ite and Black girls, respectively. Root mean square errors (RMSE) ranged fr om 1.14 to 1.95 kg. The equation for Black girls used Stature(2)/Resistance (R), weight, and reactance (X-c) as predictor variables; the equation for White girls used Stature(2)/R, weight, and triceps skinfold thickness. The results indicate that (1) equations to predict FFM in girls should be ethni c specific and that (2) accurate values for TBF and %BF can be calculated f rom the predicted FFM. Am. J. Hum. Biol. 13:249-254, 2001. (C) 2001 Wiley-L iss, Inc.