title: The combined influence of genetic factors and sedentary activity on body mass changes from adolescence to young adulthood: the National Longitudinal Adolescent Health Study.
abstract: BACKGROUND
  an increase in sedentary activities is likely a major contributor to the rise in obesity over the last three decades. Little research has examined interactions between genetic variants and sedentary activity on obesity phenotypes. High levels of sedentary activity during adolescence may interact with genetic factors to influence body mass changes between adolescence and young adulthood, a high risk period for weight gain.
  
  
  METHODS
  in the National Longitudinal Study of Adolescent Health, siblings and twin pairs (16.5 ± 1.7 years) were followed into young adulthood (22.4 ± 1.8 years). Self-reported screen time (TV, video, and computer use in h/week) and body mass index (kg/m(2) ), calculated from measured height and weight at adolescence and at young adulthood, were available for 3795 participants. We employed a variance component approach to estimate the interaction between genotype and screen time for body mass changes. Additive genotype-by-screen time interactions were assessed using likelihood-ratio tests. Models were adjusted for race, age, sex, and age-by-sex interaction.
  
  
  RESULTS
  the genetic variation in body mass changes was significantly larger in individuals with low ( δ(G) = 27.59 ± 1.58) compared with high (δ(G) = 18.76 ± 2.59) levels of screen time (p < 0.003) during adolescence.
  
  
  CONCLUSIONS
  Our findings demonstrate that sedentary activities during adolescence may interact with genetic factors to influence body mass changes between adolescence and young adulthood. Accounting for obesity-related behaviours may improve current understanding of the genetic variation in body mass changes.
authors.affiliation: Department of Nutrition, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, 27516-3997 USA.
authors.forename: M
authors.initials: M
authors.lastname: Graff
authors.forename: K E
authors.initials: KE
authors.lastname: North
authors.forename: K L
authors.initials: KL
authors.lastname: Monda
authors.forename: E M
authors.initials: EM
authors.lastname: Lange
authors.forename: L A
authors.initials: LA
authors.lastname: Lange
authors.forename: G
authors.initials: G
authors.lastname: Guo
authors.forename: P
authors.initials: P
authors.lastname: Gordon-Larsen
mesh_terms: D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D001835:Body Weight; D002648:Child; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009765:Obesity / Q000209:etiology*; D057185:Sedentary Behavior; D035781:Siblings; D014427:Twins; D015430:Weight Gain; D055815:Young Adult