Waist circumference-to-height ratio predicts adiposity better than body mass index in children and adolescents.

Body mass index (BMI) is the surrogate measure of adiposity most commonly employed in children and adults. Waist circumference (WC) and the waist circumference-to-height ratio (WCHt) have been proposed as markers of adiposity-related morbidity in children. However, no study to date has compared WCHt, WC, BMI and skinfolds thickness for their ability to detect body adiposity. To compare WCHt, WC, BMI and skinfolds for their accuracy in predicting percent body fat (PBF), percent trunk fat (PTF) and fat mass index (FMI) in a large sample of children and adolescents. We studied 2339 children and adolescents aged 8-18 years from the US National Health and Nutrition Examination Survey 2003/2004. Body fat was measured using dual-energy X-ray absorptiometry. Multivariable regression splines were used to model the association between PBF, PTF, FMI and the predictors of interest. WCHt alone explained 64% of PBF variance as compared with 31% for WC, 32% for BMI and 72% for the sum of triceps and subscapular skinfolds (SF2) (P<0.001 for all). When age and gender were added to the predictors, the explained variance increased to 80% for the WCHt model, 72% for the WC model, 68% for the BMI model and 84% for the SF2 model. There was no practical advantage to add the ethnic group as further predictor. Similar relationships were observed with PTF and FMI. WCHt is better than WC and BMI at predicting adiposity in children and adolescents. It can be a useful surrogate of body adiposity when skinfold measurements are not available.