Comparison of body composition methods in overweight and obese children

The objective of the present study was to investigate the accuracy of percent body fat (% fat) estimates from dual-energy X-ray absorptiometry, air-displacement plethysmography ( ADP), and total body water (TBW) against a criterion four-compartment (4C) model in overweight and obese children. A volunteer sample of 30 children (18 male and 12 female), age of (mean +/- SD) 14.10 +/- 1.83 yr, body mass index of 31.6 +/- 5.5 kg/m, and % fat (4C model) of 41.2 +/- 8.2%, was assessed. Body density measurements were converted to % fat estimates by using the general equation of Siri (ADP(Siri)) (Siri WE. Techniques for Measuring Body Composition. 1961) and the age- and gender-specific constants of Lohman (ADP(Loh)) (Lohman TG. Exercise and Sport Sciences Reviews. 1986). TBW measurements were converted to % fat estimates by assuming that water accounts for 73% of fat-free mass (TBW73) and by utilizing the age- and gender-specific water contents of Lohman (TBWLoh). All estimates of % fat were highly correlated with those of the 4C model (r greater than or equal to 0.95, P < 0.001; SE <= 2.14). For % fat, the total error and mean difference +/- 95% limits of agreement compared with the 4C model were 2.50, 1.8 +/- 3.5 (ADP(Siri)); 1.82, - 0.04 +/- 3.6 (ADP(Loh)); 2.86, - 2.0 +/- 4.1 (TBW73); 1.90, - 0.3 +/- 3.8 (TBWLoh); and 2.74, 1.9 +/- 4.0 DXA (dual-energy X-ray absorptiometry), respectively. In conclusion, in overweight and obese children, ADP(Loh) and TBWLoh were the most accurate methods of measuring % fat compared with a 4C model. However, all methods under consideration produced similar limits of agreement.