title: [Genetic and environmental contributions to body mass index in a Spanish adolescent twin sample].
abstract: OBJECTIVE
  Twin and family studies support large genetic influences on variability in body mass index (BMI), with heritability estimates ranging from 47% to over 90%. Our objective was to study the relative contributions of genetics and environment to BMI, evaluating sex differences, in an adolescent twin sample from Valencia, Spain.
  
  
  METHODS
  Five hundred eighty-four pairs of adolescent twins between 13 and 18 years of age completed the study (82 monozygotic [MZ] and 87 dizygotic [DZ] pairs of male twins, 118 MZ and 102 DZ pairs of female twins, and 195 opposite-sex pairs of DZ twins). To determine zygosity, teachers responded a questionnaire on physical similarity. They also measured the participant's height and weight. BMI was calculated and weight status was determined according to age. We used twin models to assess genetic and environmental (common and unique) factors affecting BMI.
  
  
  RESULTS
  There was a 7.1% frequency of overweight and 2.8% of obesity. The estimated heritability of BMI was 88.0% in boys and 72.1% in girls, with the remaining variance attributable to non-shared environment in boys (12.0%) and 8.8% in girls. It was only in girls that common environment had an effect on BMI.
  
  
  CONCLUSIONS
  Genetics appears to play an important role in explaining the variability in BMI in the adolescence, with slight variations between boys and girls. Common environmental factors exert their influence on BMI only in girls.
authors: Servicio de Psiquiatría, Hospital Universitario y Politécnico La Fe, Valencia, España. Electronic address: iranzotatay@hotmail.com.
authors: Carmen
authors: C
authors: Iranzo-Tatay
authors: Grupo de investigación Psiquiátrica, Sección de Psiquiatría Infanto-Juvenil, Hospital Universitario La Fe, Valencia, España.
authors: Natalia
authors: N
authors: Gimeno-Clemente
authors: Servicio de Psiquiatría, Hospital Universitario y Politécnico La Fe, Valencia, España; Consorcio de Investigación Biomédica de Epidemiología y Salud Pública (CIBERESP); Departamento de Psiquiatría, Facultad de Medicina, Universidad de Valencia, Valencia, España.
authors: Lorenzo
authors: L
authors: Livianos-Aldana
authors: Servicio de Psiquiatría, Hospital Universitario y Politécnico La Fe, Valencia, España; Consorcio de Investigación Biomédica de Epidemiología y Salud Pública (CIBERESP); Departamento de Psiquiatría, Facultad de Medicina, Universidad de Valencia, Valencia, España.
authors: Luis
authors: L
authors: Rojo-Moreno
mesh_terms: D000293:Adolescent; D015992:Body Mass Index; D005260:Female; D059647:Gene-Environment Interaction; D006801:Humans; D008297:Male; D009752:Nutritional Status; D009765:Obesity / Q000453:epidemiology; D050177:Overweight / Q000453:epidemiology; D013030:Spain / Q000453:epidemiology; D011795:Surveys and Questionnaires; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic
keywords: Adolescentes; Adolescents; Body mass index; Estado nutricional; Gemelos; Genetics; Genética; Twins; Weight status; Índice de masa corporal