[Methods of body composition and four compartiments model in obese school children]

In Chile, the prevalence of obesity in schoolchildren is 21.3%. The study and individual intervention of this malnutrition, it is necessary to have not only global indicators of nutritional status, but also indicators that give information on body composition.

To compare estimates of body fat isotopic dilution, plethysmography and radiographic absorptiometry 4C model in overweight schoolchildren.

We worked with 61 obese (BMI ≥ p 95) of both sexes, between 8 and 13 years, enrolled in a school in a district of the city of Santiago. The multicompartmental body composition determination, considered isotopic dilution, plethysmography and radiographic absorptiometry. Using as a reference standard four compartment model of Fuller.

In both sexes, the method showed better agreement with the reference of 4 compartments was isotope dilution (r = 0.98, p < 0.01). In children, the isotopic dilution underestimates body fat in -0.40 kg. By contrast, DEXA and plethysmography overestimate body fat by 0.81 kg and 1.89 kg respectively. In women, all methods overestimate body fat, with less emphasis isotopic dilution value 0.46 kg, 0.52 kg after DEXA and plethysmography 1.31 kg.

The deuterium isotopic dilution would be the most sensitive method for estimating body fat in research studies because it shows the best agreement with the gold standard multicompartmental model.