title: Relationship of body mass index and psychosocial factors on physical activity in underserved adolescent boys and girls.
abstract: OBJECTIVE
  Previous research indicates that body mass index (BMI) and sex are important factors in understanding physical activity (PA) levels. The present study examined the influence of BMI on psychosocial variables (self-efficacy, social support) and PA in underserved (ethnic minority, low income) boys in comparison with girls.
  
  
  METHODS
  Participants (N = 669; 56% girls; 74% African American) were recruited from the "Active by Choice Today" trial.
  
  
  METHODS
  BMI ʐ score was calculated from objectively collected height and weight data, and PA was assessed with 7-day accelerometry estimates. Self-report questionnaires were used to measure self-efficacy and social support (family, peers) for PA.
  
  
  RESULTS
  A 3-way interaction between BMI z score, sex, and family support on PA was shown such that family support was positively associated with PA in normal-weight but not overweight or obese boys, and was not associated with PA in girls. Self-efficacy had the largest effect size related to PA in comparison with the other psychosocial variables studied.
  
  
  CONCLUSIONS
  Self-efficacy was found to be an important variable related to PA in underserved youth. Future studies should evaluate possible barriers to PA in girls, and overweight youth, to provide more effective family support strategies for underserved adolescents' PA.
authors.affiliation: Department of Family Medicine, Primary Care Research Institute, University of North Texas Health Science Center, 855 Montgomery Street, Ft. Worth, TX 76107, USA. heather.kitzman-ulrich@unthsc.edu
authors.forename: Heather
authors.initials: H
authors.lastname: Kitzman-Ulrich
authors.forename: Dawn K
authors.initials: DK
authors.lastname: Wilson
authors.forename: M Lee
authors.initials: ML
authors.lastname: Van Horn
authors.forename: Hannah G
authors.initials: HG
authors.lastname: Lawman
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology; D001741:Black or African American / Q000523:psychology* / Q000706:statistics & numerical data; D015992:Body Mass Index; D002648:Child; D016000:Cluster Analysis; D015444:Exercise / Q000502:physiology / Q000523:psychology; D005190:Family / Q000523:psychology*; D005260:Female; D054624:Health Status Disparities; D006801:Humans; D016015:Logistic Models; D008297:Male; D009043:Motor Activity; D009765:Obesity / Q000208:ethnology / Q000523:psychology; D010379:Peer Group; D010809:Physical Fitness / Q000523:psychology*; D020377:Self Efficacy; D012737:Sex Factors; D012944:Social Support; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires