title: Genetic and environmental contributions to weight, height, and BMI from birth to 19 years of age: an international study of over 12,000 twin pairs.
abstract: OBJECTIVE
  To examine the genetic and environmental influences on variances in weight, height, and BMI, from birth through 19 years of age, in boys and girls from three continents.
  
  
  METHODS
  Cross-sectional twin study. Data obtained from a total of 23 twin birth-cohorts from four countries: Canada, Sweden, Denmark, and Australia. Participants were Monozygotic (MZ) and dizygotic (DZ) (same- and opposite-sex) twin pairs with data available for both height and weight at a given age, from birth through 19 years of age. Approximately 24,036 children were included in the analyses.
  
  
  RESULTS
  Heritability for body weight, height, and BMI was low at birth (between 6.4 and 8.7% for boys, and between 4.8 and 7.9% for girls) but increased over time, accounting for close to half or more of the variance in body weight and BMI after 5 months of age in both sexes. Common environmental influences on all body measures were high at birth (between 74.1-85.9% in all measures for boys, and between 74.2 and 87.3% in all measures for girls) and markedly reduced over time. For body height, the effect of the common environment remained significant for a longer period during early childhood (up through 12 years of age). Sex-limitation of genetic and shared environmental effects was observed.
  
  
  CONCLUSIONS
  Genetics appear to play an increasingly important role in explaining the variation in weight, height, and BMI from early childhood to late adolescence, particularly in boys. Common environmental factors exert their strongest and most independent influence specifically in pre-adolescent years and more significantly in girls. These findings emphasize the need to target family and social environmental interventions in early childhood years, especially for females. As gene-environment correlation and interaction is likely, it is also necessary to identify the genetic variants that may predispose individuals to obesity.
authors.affiliation: Institute of Population Health, University of Ottawa, Ottawa, Ontario, Canada. lise.dubois@uottawa.ca
authors.forename: Lise
authors.initials: L
authors.lastname: Dubois
authors.forename: Kirsten
authors.initials: K
authors.lastname: Ohm Kyvik
authors.forename: Manon
authors.initials: M
authors.lastname: Girard
authors.forename: Fabiola
authors.initials: F
authors.lastname: Tatone-Tokuda
authors.forename: Daniel
authors.initials: D
authors.lastname: Pérusse
authors.forename: Jacob
authors.initials: J
authors.lastname: Hjelmborg
authors.forename: Axel
authors.initials: A
authors.lastname: Skytthe
authors.forename: Finn
authors.initials: F
authors.lastname: Rasmussen
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: Wright
authors.forename: Paul
authors.initials: P
authors.lastname: Lichtenstein
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: Martin
mesh_terms: D000293:Adolescent; D001315:Australia; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D002170:Canada; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D003718:Denmark; D005260:Female; D059647:Gene-Environment Interaction; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D013548:Sweden; D014427:Twins; D055815:Young Adult