title: Associations between physical activity, body fat, and insulin resistance (homeostasis model assessment) in adolescents: the European Youth Heart Study.
abstract: BACKGROUND
  More and better data are needed to understand the action of physical activity (PA) on insulin resistance and the concomitant relation with body fat in adolescence.
  
  
  OBJECTIVE
  We examined the relation between total PA and intensity levels with insulin resistance under special consideration of waist circumference and skinfold thickness.
  
  
  METHODS
  This was a cross-sectional study of 613 adolescents (352 girls, 261 boys) with a mean (+/-SD) age of 15.5 +/- 0.5 y from Sweden and Estonia. Total, low, moderate, and vigorous PA was measured by accelerometry. Body fat estimators included waist circumference and the sum of 5 skinfold thicknesses. Fasting insulin and glucose were measured, and insulin resistance was calculated according to the homeostasis model assessment (HOMA). Linear regression analysis and analysis of covariance were used to determine the association between PA and insulin resistance while considering body fat. All estimates were adjusted for sex, country, pubertal status, and indicators of body fat when applicable.
  
  
  RESULTS
  Total, moderate, and vigorous PA were inversely correlated with HOMA. Body fat estimators were positively correlated with HOMA. Significant contrasts in HOMA concentrations were seen when comparing the lower 2 tertiles with the upper tertile of PA indicators. Repeating the analysis with body fat estimators showed significant contrasts in HOMA concentrations when comparing the lower tertiles with the upper tertile.
  
  
  CONCLUSIONS
  In view of an increase in obesity in young people, the results accentuate the role of PA in sustaining metabolic balance in adolescence and the potential benefit of an increase of time spent at higher PA levels for youth with relatively elevated amounts of body fat.
authors.affiliation: Unit for Preventive Nutrition, Department of Biosciences and Nutrition, NOVUM, Karolinska Institutet, Huddinge, Sweden. nico.rizzo@biosci.ki.se
authors.forename: Nico S
authors.initials: NS
authors.lastname: Rizzo
authors.forename: Jonatan R
authors.initials: JR
authors.lastname: Ruiz
authors.forename: Leila
authors.initials: L
authors.lastname: Oja
authors.forename: Tomas
authors.initials: T
authors.lastname: Veidebaum
authors.forename: Michael
authors.initials: M
authors.lastname: Sjöström
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000293:Adolescent; D000704:Analysis of Variance; D001786:Blood Glucose / Q000378:metabolism; D001823:Body Composition / Q000502:physiology; D003431:Cross-Cultural Comparison; D003430:Cross-Sectional Studies; D004957:Estonia / Q000453:epidemiology; D015444:Exercise / Q000502:physiology*; D005215:Fasting / Q000097:blood; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D016014:Linear Models; D008297:Male; D009765:Obesity / Q000378:metabolism* / Q000517:prevention & control; D010809:Physical Fitness / Q000502:physiology*; D012885:Skinfold Thickness; D013548:Sweden / Q000453:epidemiology; D049629:Waist-Hip Ratio
chemical_list: D001786:Blood Glucose; D007328:Insulin