title: Associations between physical activity and fat mass in adolescents: the Stockholm Weight Development Study.
abstract: BACKGROUND
  Obesity is multifactorial. However, the accumulation of fat mass (FM) is proposed to be due to a positive energy balance, which may be caused by reduced physical activity (PA).
  
  
  OBJECTIVE
  The objectives of the study were to describe the independent associations between PA and FM in adolescents and to describe the intergenerational association of FM between mothers and their offspring.
  
  
  METHODS
  We conducted a cross-sectional study in 445 (190 M, 255 F) 17-y-old adolescents and their mothers. PA was assessed with a self-reported questionnaire and validated by comparison with accelerometric data in a subsample of the cohort. Body composition was measured by using air-displacement plethysmography.
  
  
  RESULTS
  Males were significantly more active than were females (P<0.01). PA was significantly and inversely associated with FM (beta=-3.63, P=0.005) and percentage FM (beta=-3.117, P=0.017) in males but not in females (beta=-0.576, P=0.54; beta=-0.532, P=0.59, respectively) after adjustment for birth weight and maternal FM and education level. However, FM and percentage FM in females were significantly associated with maternal FM (beta=0.159, P<0.0001; beta=0.145, P=0.002, respectively) and education level (beta=-1.048, P<0.005; beta=-1.085, P=0.006, respectively). No such associations were observed in males.
  
  
  CONCLUSIONS
  PA was independently associated with FM in males but not in females. The data also showed an intergenerational association of FM between mothers and their daughters but not between mothers and their sons.
authors.affiliation: Medical Research Council Epidemiology Unit, Cambridge, United Kingdom. ue202@medschl.cam.ac.uk
authors.forename: Ulf
authors.initials: U
authors.lastname: Ekelund
authors.forename: Martin
authors.initials: M
authors.lastname: Neovius
authors.forename: Yvonné
authors.initials: Y
authors.lastname: Linné
authors.forename: Søren
authors.initials: S
authors.lastname: Brage
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Wareham
authors.forename: Stephan
authors.initials: S
authors.lastname: Rössner
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000293:Adolescent; D000886:Anthropometry; D001823:Body Composition / Q000502:physiology*; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004734:Energy Metabolism / Q000235:genetics / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009035:Mothers; D009765:Obesity / Q000453:epidemiology / Q000209:etiology* / Q000378:metabolism; D010993:Plethysmography, Whole Body / Q000379:methods; D012650:Self Disclosure; D012737:Sex Factors; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology