Body composition techniques and the four-compartment model in children

Abstract

Fields, David A., and Michael I. Goran. Body composition techniques and the four-compartment model in children. J Appl Physiol 89: 613-620, 2000.-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 Ϯ 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 ϭ 0.84 ϫ FM by DXA ϩ 0.95 kg; R 2 ϭ 0.95), as did the regression between FM by 4C model and by TBW (FM by 4C model ϭ 0.85 ϫ FM by TBW Ϫ 0.89 kg; R 2 ϭ 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 ϭ 1.09 ϫ FM by HW ϩ 0.94 kg; R 2 ϭ 0.95) and neither did the regression between FM by 4C (using density assessed by PM) and by PM (FM by 4C model ϭ 1.03 ϫ FM by PM ϩ 0.88; R 2 ϭ 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 CHILDHOOD OBESITY IS INCREASING at an alarming rate and is predictive of adulthood obesity (9,12,26), with deleterious effects on future health status (6,9,15,26). The increasing obesity and strong relation with health risk highlight the importance of identifying accurate techniques for measuring total body fat in children. Accurate techniques are required both for clinical tracking and for monitoring for laboratory-based research studies.Two-compartment (2C) models, such as total body water (TBW) and densitometry, are commonly used to evaluate body composition in children. This approach, however, may not be the most accurate in children because of potential changes in the various inherent assumptions of 2C techniques during growth and maturation, such as changes in the hydration and the density of the fat-free mass (16). Baumgartner et al. (1) have suggested that the four-compartment model (4C model) be used as the "gold standard" in adults and the Lohman equation (17), against which other body composition techniques are to be evaluated, in children. This multicompartment approach involves independent assessment of body density, body water, and bone. This approach can account for deviations in the quality of fat-free mass, in part, because the 4C model measures the individual constituents of the fat-free mass (aqueous and bone) rather than assuming a constant density of 1.100 g/cm 3 and hydration of 73.2%. Although this multicompartment approach is preferred, it is impractical for most laboratories because of the cost and necessary equipment needed to measure TBW and bone mineralization. Although the advantages of the 4C model are numerous, it has not been widely used or compare...

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