title: Gender differences in physical activity, sedentary behavior, and their relation to body composition in active Brazilian adolescents.
abstract: BACKGROUND
  Body weight and composition are determined by genotype, environment, and energy balance. Physical activity or sedentary behavior have different associations with body weight, fat mass, and fat-free mass, a relationship that is not clear in adolescents. The aim of this study was to test the associations between gender, physical activity, sedentary behavior, and body composition in physically active adolescents.
  
  
  METHODS
  Weight, height, and skinfold thickness were measured in 326 physically active boys and girls age 11 to 15 years. All subjects answered a questionnaire assessing their usual daily activities for the last month. Time spent on each activity was used to estimate the physical activity level (PAL).
  
  
  RESULTS
  PAL was associated with body composition after adjustment for age and maturation, with differences between genders. For boys, PAL was positively and significantly associated with body mass index (BMI) and fat-free mass index (beta=0.14 and 0.15, respectively). For girls, PAL was negatively and significantly associated with BMI and fat mass index (beta=-0.11 and -0.75, respectively). Sedentary behavior, expressed by hours of TV, videogame, and computer use, was not associated with any body-composition outcome for either gender.
  
  
  CONCLUSIONS
  The accumulated amount of physical activity, but not of sedentary behavior, was related to body composition in active adolescents.
authors.affiliation: College of Physical Education, Department of Nutrition, University of Brasília, Brazil.
authors.forename: Julia Aparecida Devide
authors.initials: JA
authors.lastname: Nogueira
authors.forename: Teresa Helena
authors.initials: TH
authors.lastname: Macedo da Costa
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D001823:Body Composition; D001827:Body Height; D001835:Body Weight; D001938:Brazil / Q000453:epidemiology; D002648:Child; D002652:Child Behavior; D005260:Female; D006801:Humans; D007899:Leisure Activities; D016014:Linear Models; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D012737:Sex Factors; D012885:Skinfold Thickness; D011795:Surveys and Questionnaires