title: Gender composition of preadolescents' friendship groups moderates peer socialization of body change behaviors.
abstract: OBJECTIVE
  Peer socialization may be an important contributor to the rising prevalence of diet and muscle gain behaviors (i.e., body change behaviors) in adolescence. The present study longitudinally examined body change behaviors in preadolescents' friendship groups as predictors of preadolescents' own body change behaviors. It was predicted that peer socialization effects would vary according to the gender composition of preadolescents' friendship group.
  
  
  METHODS
  Participants (N = 648, 48.8% female) were in grades 6 through 8 at Time 1 and reported their dieting and muscle-gaining behavior at three time points approximately 1 year apart. Friendship groups were identified from preadolescents' friendship nominations. Body mass index and pubertal timing were included in analyses as control variables. A multiple group latent growth curve model was used to examine hypotheses.
  
  
  RESULTS
  Socialization of body change behaviors in preadolescent friendship groups was observed only under certain conditions. For members of all-male friendship groups, preadolescents' dieting trajectories were predicted from friends' average level of dieting.
  
  
  CONCLUSIONS
  Peer socialization effects are associated with trajectories of preadolescents' body change behaviors, particularly among all-male groups. Future research would benefit from incorporating the friendship group context into the study of health risk behaviors in preadolescents.
authors.affiliation: Department of Psychology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3270, USA. dmrancourt@gmail.com
authors.forename: Diana
authors.initials: D
authors.lastname: Rancourt
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Conway
authors.forename: William J
authors.initials: WJ
authors.lastname: Burk
authors.forename: Mitchell J
authors.initials: MJ
authors.lastname: Prinstein
mesh_terms: D000293:Adolescent; D002648:Child; D004032:Diet / Q000523:psychology*; D015444:Exercise / Q000523:psychology*; D005260:Female; D033062:Friends / Q000523:psychology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009132:Muscles / Q000502:physiology*; D010379:Peer Group; D012737:Sex Factors; D012951:Socialization