A novel approach to assess body composition in children with obesity from density of the fat-free mass

SummaryBackground & aims Assessment of Fat Mass (FM) and fat-free mass (FFM) using Air-displacement plethysmography (ADP) technique assumes constant density FFM (DFFM) by age sex. It has been recently shown that DFFM further varies according to body index (BMI), meaning ADP composition assessments children with obesity could be biased if is assumed constant. The aim this study was validate the use calculations (rather than FFM) improve accuracy assessment in obesity. Methods cross-sectional validation 66 (aged 8–14 years) where assuming (FFMBODPOD FMBODPOD) were compared those adjusted relation BMI (FFMadjusted FMadjusted), both gold standard reference, 4-component model (FFM4C FM4C). Results FFMBODPOD overestimated 1.50 kg (95%CI -0.68 kg, 3.63 kg) while FFMadjusted 0.71 (−1.08 2.51 (percentage differences FFM4C 4.9% (±2.9%) 2.8% (±2.1%), respectively (p < 0.001)). Consistently, FM underestimated methods, representing a mean difference between methods 4.0% 6.8% (±3.8%), respectively, when reference method. agreement reliability improved (adjusted models) rather DFFM. Conclusions values for properties may increase bias assessing (FM two-component techniques such as ADP. Using corrections proposed present work reduce half.