Body composition techniques and the four-compartment model in children

Division of Physiology and Metabolism, Department of Nutrition Sciences, and The Clinical Nutrition Research Unit, University of Alabama at Birmingham, Birmingham, Alabama 35294 The purpose of this study was to compare the accuracy, precision, and bias of fat mass (FM) as assessed by dual-energy X-ray absorptiometry (DXA), hydrostatic weighing (HW), air-displacement plethysmography (PM) using the BOD POD body composition system and total body water (TBW) against the four-compartment (4C) model in 25 children (11.4 ± 1.4 yr). The regression between FM by the 4C model and by DXA deviated significantly from the line of identity (FM by 4C model = 0.84 × FM by DXA + 0.95 kg; R 2 = 0.95), as did the regression between FM by 4C model and by TBW (FM by 4C model = 0.85 × FM by TBW 0.89 kg; R 2 = 0.98). The regression between FM by the 4C model and by HW did not significantly deviate from the line of identity (FM by 4C model = 1.09 × FM by HW + 0.94 kg; R 2 = 0.95) and neither did the regression between FM by 4C (using density assessed by PM) and by PM (FM by 4C model = 1.03 × FM by PM + 0.88; R 2 = 0.97). DXA, HW, and TBW all showed a bias in the estimate of FM, but there was no bias for PM. In conclusion, PM was the only technique that could accurately, precisely, and without bias estimate FM in 9- to 14-yr-old children. total body water; hydrostatic weighing; plethysmography