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 (TBW_Loh). All estimates of %fat were highly correlated with those of the 4C model (r ≥ 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 (TBW_Loh); and 2.74, 1.9 ± 4.0 DXA (dual-energy X-ray absorptiometry), respectively. In conclusion, in overweight and obese children, ADP_Loh and TBW_Loh were the most accurate methods of measuring %fat compared with a 4C model. However, all methods under consideration produced similar limits of agreement.