title: Prevalence and trends of underweight and BMI distribution changes in Japanese teenagers based on the 2001 National Survey data.
abstract: BACKGROUND
  Excessive thinness has been glamorized among Japanese adolescent girls, and unhealthy dieting to lose weight has become a popular practice among them. The prevalence of underweight in contemporary Japanese girls in comparison with that of boys, however, remains to be studied.
  
  
  OBJECTIVE
  The purpose of this study was to determine the prevalence and trends of underweight in contemporary Japanese teenagers of both sexes using nationally representative cross-sectional data.
  
  
  METHODS
  Underweight was defined as BMI < 3rd percentile by age and sex of the 1978-1981 reference population as previously reported. These reference values were compared with BMIs of the contemporary population based on the 2001 Cross-sectional National Survey data of Japanese teenagers (215 972 boys and 216 496 girls).
  
  
  RESULTS
  The prevalence of underweight was approximately 2-3% in junior high school students of both sexes, 12.5-14.5 years of age, approximately 3% in senior high school students of both sexes, 15.5-16.5 years of age, and approximately 4% in senior high school students of both sexes, 17.5 years of age.
  
  
  CONCLUSIONS
  The prevalence of underweight decreased among Japanese teenage students of both sexes during the past decades. Female preponderance in the prevalence of underweight was not confirmed.
authors.affiliation: Department of Pediatrics, Keio University School of Medicine. Tokyo, Japan.
authors.forename: Mikako
authors.initials: M
authors.lastname: Inokuchi
authors.forename: Nobutake
authors.initials: N
authors.lastname: Matsuo
authors.forename: John I
authors.initials: JI
authors.lastname: Takayama
authors.forename: Tomonobu
authors.initials: T
authors.lastname: Hasegawa
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D011159:Population Surveillance / Q000379:methods*; D015995:Prevalence; D012016:Reference Values; D017678:Sex Distribution; D013851:Thinness / Q000453:epidemiology*