The four-compartment model of body composition in obese Chilean schoolchildren, by pubertal stage: comparison with simpler models.

OBJECTIVES We assessed the agreement of body fat and fat-free mass measured by simpler methods against the four-compartment model (4C). METHODS In 60 obese schoolchildren (body mass index ≥95th percentile) between the ages of 8 and 13 y who were recruited from one school in Chile, multicompartmental body composition was estimated with the use of isotopic dilution, plethysmography (BodPod), radiographic absorptiometry (DEXA), and anthropometric equations. These results were compared to those of the 4C model, which is considered the gold standard. RESULTS For body fat, the 4C model showed the best agreement with DEXA for boys in Tanner stages I and II (r = 0.971) and with isotopic dilution for boys in Tanner stages III and IV (r = 0.984). The best agreement in girls occurred with isotopic dilution, regardless of pubertal stage (r = 0.948 for Tanner stages I and II; r = 0.978 for Tanner stages III and IV). Both isotopic dilution and the Huang, Ellis, and Deurenberg anthropometric equations underestimated body fat in boys; by contrast, DEXA, BodPod, and the Slaughter equation overestimated body fat in boys. All of the equations underestimated body fat in girls. For fat-free mass in both boys and girls, the 4C model showed the best agreement with isotopic dilution, regardless of pubertal stage. The Huang equation showed the best agreement for boys (r = 0.730 for Tanner stages I and II; r = 0.695 for Tanner stages III and IV) and for girls in Tanner stages I and II (r = 0.884). The Ellis equation had the best agreement for girls in Tanner stages III and IV (r = 0.917). CONCLUSIONS For obese Chilean children of both sexes, isotopic dilution and DEXA were the two-compartment methods that had the best agreement with the gold-standard 4C model for both body fat and fat-free mass; these were followed by the Huang and Ellis anthropometric equations.