Prediction of fat-free body mass from bioelectrical impedance among 9-to 11-year-old Swedish children

Aim: Predictive equations for estimating body composition from bioelectrical impedance analysis (BIA) among Scandinavian children are lacking. In the present study, equations for estimation of fat-free body mass (FFM) and lean tissue mass (LTM) were developed and cross-validated from BIA using dual-energy X-ray absorptiometry (DXA) as the reference measurement of body composition. Methods: The study population consisted of 49 girls and 52 boys aged 9-11 years from Malmo, Sweden. Bioelectrical impedance was measured between hand and foot at 50 kHz. Predictive equations were developed by multiple linear regression and cross-validated against DXA measurements of body composition. Results: FFM was predicted from BIA and anthropometric variables with an adjusted R-2 = 0.95 and root mean square error (RMSE) = 0.84 kg, and LTM was predicted with an adjusted R-2 = 0.95 and RMSE = 0.87 kg. Cross-validation revealed a mean RMSE = 0.95 kg FFM and a mean RMSE = 0.96 kg LTM. Prediction of body composition from equations developed in previous literature was mixed when applied to the present cohort of children. Conclusions: FFM and LTM are predicted with sufficient accuracy at the population level. We recommend that the predictive equations developed in the present study are used in prepubescent European children aged 9-11 years only in order to minimize confounding of results because of possible differences in population samples