title: Twins and virtual twins: bases of relative body weight revisited.
abstract: OBJECTIVE
  Application of a new investigative strategy to assess genetic and environmental influences on relative body weight.
  
  
  METHODS
  Covariance structure analysis of body mass index (BMI) using genetically informative samples.
  
  
  METHODS
  One-hundred and fourteen monozygotic (MZ) twin pairs (age 5.04-22.93 y), 81 dizygotic (DZ) twin pairs (age 6.05-16.52 y), and 98 virtual twin (VT) pairs, ie same-age unrelated siblings (3.68-54.75 y).
  
  
  METHODS
  Height, weight, BMI variously obtained by direct measurement and self-report.
  
  
  RESULTS
  In contrast with most previous studies, significant common environmental influence on BMI was observed.
  
  
  CONCLUSIONS
  Much past research may have underestimated common environmental effects on BMI because the designs lacked the power or ability to detect them.
authors.affiliation: Department of Psychology and Twin Studies Center, California State University, Fullerton 92834, USA. nsegal@fullerton.edu
authors.forename: N L
authors.initials: NL
authors.lastname: Segal
authors.forename: D B
authors.initials: DB
authors.lastname: Allison
mesh_terms: D000300:Adoption; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight / Q000235:genetics*; D004777:Environment; D006801:Humans; D014427:Twins; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic