title: Fat and lean BMI reference curves in children and adolescents and their utility in identifying excess adiposity compared with BMI and percentage body fat.
abstract: BACKGROUND
  Body mass index (BMI) and percentage body fat (%BF) are widely used to assess adiposity. These indexes fail to account for independent contributions of fat mass (FM) and lean body mass (LBM) to body weight, which vary according to age, sex, pubertal status, and population ancestry in the pediatric population.
  
  
  OBJECTIVE
  The objective was to develop pediatric reference curves for fat mass index (FMI) and lean body mass index (LBMI) and evaluate the effects of population ancestry and LBM on measures of excess adiposity (BMI, %BF, and FMI).
  
  
  METHODS
  Sex-specific FMI and LBMI reference curves relative to age for children and adolescents aged 8-20 y were generated from cross-sectional body-composition data measured by dual-energy X-ray absorptiometry from NHANES.
  
  
  RESULTS
  The mean LBMI z score was higher in blacks (males: 0.26; females: 0.45) than in whites (males: -0.07; females: -0.09) and Mexican Americans (males: 0.05; females: -0.09). The positive predictive value of overweight by BMI to identify excess adiposity defined by FMI was lower in blacks (males: 35.9%; females: 30.3%) than in whites (males: 65.4%; females: 52.2%) and Mexican Americans (males: 73.3%; females: 68.3%). Participants classified as having excess adiposity by FMI but normal adiposity by %BF had significantly higher BMI, LBMI, and height z scores than did those classified as having excess adiposity by %BF but normal adiposity by FMI.
  
  
  CONCLUSIONS
  Relative to FMI, the prevalence of excess adiposity is overestimated by BMI in blacks and underestimated by %BF in individuals with high LBM. The use of FMI and LBMI improves on the use of %BF and BMI by allowing for the independent assessment of FM and LBM.
authors.affiliation: Department of Pediatrics, The Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Weber
authors.forename: Reneé H
authors.initials: RH
authors.lastname: Moore
authors.forename: Mary B
authors.initials: MB
authors.lastname: Leonard
authors.forename: Babette S
authors.initials: BS
authors.lastname: Zemel
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue; D050154:Adiposity; D000293:Adolescent; D044383:Black People; D001823:Body Composition; D015992:Body Mass Index; D001835:Body Weight; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D017058:Mexican Americans; D009749:Nutrition Surveys; D009765:Obesity / Q000453:epidemiology; D011237:Predictive Value of Tests; D015995:Prevalence; D012016:Reference Values; D014481:United States / Q000453:epidemiology; D044465:White People; D055815:Young Adult; D001741:Black or African American