title: How are physical activity, fitness, and sedentary behavior associated with insulin sensitivity in children?
abstract: OBJECTIVE
  To describe the associations among moderate-to-vigorous physical activity (MVPA), fitness, sedentary behavior (SB), and insulin sensitivity (IS).
  
  
  METHODS
  Data were drawn from the baseline assessment of the QUALITY cohort, which included 630 white youth (aged 8-10 years at recruitment), with at least one obese biological parent. IS was measured by two fasting indices (insulin, homeostasis model assessment of insulin resistance) and an oral glucose tolerance test (OGTT)-based index (Matsuda IS index [Matsuda-ISI]). Fitness was measured by Vo(2peak); percent fat mass (PFM) was measured by dual-energy X-ray absorptiometry; 7-day MVPA was measured with accelerometry. SB indicators included average hours daily of self-report screen time (SBst), and average minutes daily at <100 counts/min from accelerometry (SBacc). Multivariable linear regression models were adjusted for age, sex, season, and puberty.
  
  
  RESULTS
  MVPA and SBacc were independently associated with IS, but this was no longer statistically significant after accounting for PFM. SBst was negatively associated with IS in girls only, even after controlling for physical activity (PA), fitness, and adiposity; for each additional hour of SBst daily, IS decreased by 4.6-5.6% across all IS indices. Fitness was positively associated with IS (measured by Matsuda-ISI) after accounting for PA, SB, and PFM; for every 1 unit increase in Vo(2peak), Matsuda-ISI increased by approximately 1.0% (P < 0.05).
  
  
  CONCLUSIONS
  In children with an obese parent, PA and SBacc are associated with IS, but this association is mediated by adiposity. SBst is negatively associated with IS in girls, beyond its known impact on adiposity. Finally, fitness is independently associated with better IS measured by OGTT.
authors.affiliation: Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montréal, Québec, Canada. melanie.henderson@mail.mcgill.ca
authors.forename: Mélanie
authors.initials: M
authors.lastname: Henderson
authors.forename: Katherine
authors.initials: K
authors.lastname: Gray-Donald
authors.forename: Marie-Eve
authors.initials: ME
authors.lastname: Mathieu
authors.forename: Tracie A
authors.initials: TA
authors.lastname: Barnett
authors.forename: James A
authors.initials: JA
authors.lastname: Hanley
authors.forename: Jennifer
authors.initials: J
authors.lastname: O'Loughlin
authors.forename: Angelo
authors.initials: A
authors.lastname: Tremblay
authors.forename: Marie
authors.initials: M
authors.lastname: Lambert
mesh_terms: D015502:Absorptiometry, Photon; D017668:Age of Onset; D001786:Blood Glucose / Q000378:metabolism*; D002648:Child; D016241:Child of Impaired Parents; D003430:Cross-Sectional Studies; D004734:Energy Metabolism; D015444:Exercise; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D009765:Obesity; D010809:Physical Fitness; D011237:Predictive Value of Tests; D057185:Sedentary Behavior
chemical_list: D001786:Blood Glucose