Assessment of body composition in 8-11 year old children by bioelectrical impedance.

In 64 prepubescent schoolchildren, 33 boys and 31 girls, aged 8-11 years, body composition was measured by means of anthropometry, densitometry and bioelectrical impedance. From body density the body fat percentage was calculated using age-specific density values for the fat-free mass. Boys and girls younger than 10 years did not differ in body composition. Older boys however had higher body weights, higher body densities and lower body impedance values. Fat-free mass as determined by densitometry could be predicted by body impedance and body weight with a prediction error of 1.31 kg. The prediction formula was sex-specific. Omitting the impedance in the prediction equation resulted in a 7 per cent lower explained variance and an only slightly higher prediction error of the FFM of 1.65 kg. The prediction formulas from the literature, developed in adult populations, grossly overestimated the fat-free mass in children, probably due to a different water distribution between the intra- and extra-cellular spaces.