title: Body mass index cut offs to define thinness in children and adolescents: international survey.
abstract: OBJECTIVE
  To determine cut offs to define thinness in children and adolescents, based on body mass index at age 18 years.
  
  
  METHODS
  International survey of six large nationally representative cross sectional studies on growth.
  
  
  METHODS
  Brazil, Great Britain, Hong Kong, the Netherlands, Singapore, and the United States.
  
  
  METHODS
  97 876 males and 94 851 females from birth to 25 years.
  
  
  METHODS
  Body mass index (BMI, weight/height(2)).
  
  
  RESULTS
  The World Health Organization defines grade 2 thinness in adults as BMI <17. This same cut off, applied to the six datasets at age 18 years, gave mean BMI close to a z score of -2 and 80% of the median. Thus it matches existing criteria for wasting in children based on weight for height. For each dataset, centile curves were drawn to pass through the cut off of BMI 17 at 18 years. The resulting curves were averaged to provide age and sex specific cut-off points from 2-18 years. Similar cut offs were derived based on BMI 16 and 18.5 at 18 years, together providing definitions of thinness grades 1, 2, and 3 in children and adolescents consistent with the WHO adult definitions.
  
  
  CONCLUSIONS
  The proposed cut-off points should help to provide internationally comparable prevalence rates of thinness in children and adolescents.
authors.affiliation: Centre for Paediatric Epidemiology and Biostatistics, UCL Institute of Child Health, London WC1N 1EH. tim.cole@ich.ucl.ac.uk
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Cole
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Flegal
authors.forename: Dasha
authors.initials: D
authors.lastname: Nicholls
authors.forename: Alan A
authors.initials: AA
authors.lastname: Jackson
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009765:Obesity / Q000175:diagnosis* / Q000453:epidemiology; D015995:Prevalence; D012015:Reference Standards; D013851:Thinness / Q000175:diagnosis* / Q000453:epidemiology