Determination of body composition in African-American children: validation of bioelectrical impedence with dual energy X-ray absorptiometry.

Body compositional differences between Black and White adults are well-known. It has become increasingly apparent that these racial variations may begin in childhood. Previously, our group validated tetrapolar bioelectrical impedance (BIA) measurements against H2(18O) dilution method to develop prediction formulas of fat free mass (FFM) in healthy White-American children: FFM = 0.524 Ht2/R + 0.415 Wt 0.32. In the present study we used BIA to establish a FFM prediction equation for forty African-American children (19 males and 21 females). Of the females, six were diagnosed with polycystic ovary syndrome (PCOS) and were obese. FFM was determined by dual energy X-ray absorptiometry (DEXA). Impedence measurements by BIA showed a strong correlation with FFM determined by DEXA. In healthy Black children, FFM = 0.84 Ht2/R + 1.10 with a standard error of estimate (SEE) of 1.47 kg (R2 = 0.97). In Black females with PCOS, FFM = 0.62 Ht2/R + 0.21 Wt - 1.94 with a SEE of 1.43 kg (R2 = 0.99). The observed differences in the prediction equations of FFM between White-American and African-American children underline the importance of using race-specific formulas in evaluating body composition. With the overall increase in rates of childhood obesity and more so in the Black race, BIA is an easy and useful tool for the assessment and follow up of body compositional changes with lifestyle interventions.