Comparison of body composition methods: a literature analysis

Abstract

Objective: To examine the comparability of different methods to assess percentage body fat (BF%) against underwater weighing (UWW). Design: A meta-analysis on 54 papers, published in 1985–96, on healthy, adult Caucasians. Methods: The mean BF% from different studies were treated as single data points. In addition to UWW, the studies included one or more of the following methods: 3- or 4-component model, dual-energy X-ray absorptiometry (DXA), dual-energy photon absorptiometry, isotope dilution, bioimpedance (BIA), skinfolds or near-infrared interactance (NIR). Within each of the methods, the analyses were done separately for different mathematical functions, techniques or instruments. Main outcome measures: Bias (mean difference) and error (s.d. of difference) between BF% measured by UWW and the other methods. Results: The 4-component model gave 0.6 (95% confidence interval for the mean, CI: 0.1 to 1.2) BF% higher results than UWW. Also the 3-component model with body density and total body water (+1.4 BF%, 95% CI: +0.3 to +2.6), deuterium dilution (+1.5 BF%, 95% CI: +0.7 to +2.3), DXA by Norland (+7.2 BF%, 95% CI: 2.6 to 11.8) and BIA by Lukaski et al. (+2.0 BF%, 95% CI: 0.2 to 3.8) overestimated BF%, whereas BIA by Valhalla Scientific (−2.6 BF%, 95% CI: −4.5 to −0.6) and skinfold equations by Jackson et al. (−1.20, 95% CI: −2.3 to −0.1) showed a relative underestimation. The mean bias for the skinfold equation by Durnin & Womersley, against UWW, was 0.0 BF% (95% CI: −1.3 to 1.3). The correlation between the size of measurement and the mean difference was significant for only NIR (r=−0.77, P=0.003). Conclusions: The difference between any method and UWW is dependent on the study. However, some methods have a systematical tendency for relative over- or underestimation of BF%.