title: Utility of Body Mass Index in Identifying Excess Adiposity in Youth Across the Obesity Spectrum.
abstract: 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.
  
  
  
  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.
  
  
  
  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.
  
  
  
  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.
authors: Department of Pediatrics, University of Minnesota Medical School, Minneapolis, MN.
authors: Justin R
authors: JR
authors: Ryder
authors: Division of Biostatistics, University of Minnesota School of Public Health, Minneapolis, MN.
authors: Alexander M
authors: AM
authors: Kaizer
authors: Division of Biostatistics, University of Minnesota School of Public Health, Minneapolis, MN.
authors: Kyle D
authors: KD
authors: Rudser
authors: Department of Pediatrics, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO.
authors: Stephen R
authors: SR
authors: Daniels
authors: Department of Pediatrics, University of Minnesota Medical School, Minneapolis, MN; Department of Medicine, University of Minnesota Medical School, Minneapolis, MN.
authors: Aaron S
authors: AS
authors: Kelly
mesh_terms: D015502:Absorptiometry, Photon; D050154:Adiposity; D000293:Adolescent; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000000981:diagnostic imaging / Q000453:epidemiology; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008659:Metabolic Diseases / Q000000981:diagnostic imaging / Q000453:epidemiology; D063766:Pediatric Obesity / Q000000981:diagnostic imaging*; D012307:Risk Factors; D055815:Young Adult
keywords: NHANES; adiposity; children; dual energy x-ray absorptiometry; obesity