Objectives To determine the proportion of youth within a given body mass index (BMI) obesity category with excess adiposity using dual energy x-ray absorptiometry (DXA). Furthermore, to examine whether mean differences in cardiometabolic risk factors based upon various excess adiposity cutpoints were present. Study design DXA data from the National Health and Nutrition Examination Survey 1999-2006 (n = 10 465; 8-20 years of age) were used for this analysis. Obesity categories were defined using Centers for Disease Control and prevention definitions for age and sex. Excess adiposity was defined using cohort-specific cutpoints at 75th, 85th, and 90th percentiles of DXA body fat (%) by age and sex using quantile regression models. Additionally, we examined differences in cardiometabolic risk factors among youth (BMI percentile >85th) above and below various excess adiposity cutpoints. Results Nearly all youth with class 3 obesity (100% male, 100% female; 97% male, 99% female; and 95% male, 96% female; using the 75th, 85th, and 90th DXA percentiles, respectively) and a high proportion of those with class 2 obesity (98% male, 99% female; 92% male, 91% female; and 76% male, 76% female) had excess adiposity. Significant discordance was observed between BMI categorization and DXA-derived excess adiposity among youth with class 1 obesity or overweight. Elevated cardiometabolic risk factors were present in youth with excess adiposity, regardless of the cutpoint used. Conclusions BMI correctly identifies excess adiposity in most youth with class 2 and 3 obesity but a relatively high degree of discordance was observed in youth with obesity and overweight. Cardiometabolic risk factors are increased in the presence of excess adiposity, regardless of the cutpoint used.
Bibliographical noteFunding Information:
J.R. is supported by the National Institutes of Health /National Heart, Lung, and Blood Institute ( F32-HL127851-01 ). K.R. is supported by the National Center for Advancing Translational Sciences /National Institutes of Health ( UL1TR000114 ). A.K. serves on pediatric obesity advisory boards for Takeda and Novo Nordisk; serves as an author for a pediatric obesity clinical trial sponsored by Novo Nordisk ( ClinicalTrials.gov: NCT02496611), but does not receive personal or professional income for these activities; and receives research drugs/placebo from Aztra Zeneca. S.D. serves as an Associate Editor for The Journal of Pediatrics. The other authors declare no conflicts of interest.
© 2016 Elsevier Inc.
- dual energy x-ray absorptiometry