title: Physical Activity and Pediatric Obesity: A Quantile Regression Analysis.
abstract: We aimed to determine whether moderate to vigorous physical activity (MVPA) and sedentary behavior (SB) were independently associated with body mass index (BMI) and waist circumference (WC) in children and adolescents.
  
  
  
  Data from the International Children's Accelerometry Database were used to address our objectives (N = 11,115; 6-18 yr; 51% female). We calculated age- and gender-specific BMI and WC z-scores and used accelerometry to estimate MVPA and total SB. Self-reported television viewing was used as a measure of leisure time SB. Quantile regression was used to analyze the data.
  
  
  
  MVPA and total SB were associated with lower and higher BMI and WC z-scores, respectively. These associations were strongest at the higher percentiles of the z-score distributions. After including MVPA and total SB in the same model, the MVPA associations remained, but the SB associations were no longer present. For example, each additional hour per day of MVPA was not associated with BMI z-score at the 10th percentile (b = -0.02, P = 0.170) but was associated with lower BMI z-score at the 50th (b = -0.19, P < 0.001) and 90th percentiles (b = -0.41, P < 0.001). More television viewing was associated with higher BMI and WC, and the associations were strongest at the higher percentiles of the z-score distributions, with adjustment for MVPA and total SB.
  
  
  
  Our observation of stronger associations at the higher percentiles indicates that increasing MVPA and decreasing television viewing at the population-level could shift the upper tails of the BMI and WC frequency distributions to lower values, thereby lowering the number of children and adolescents classified as obese.
authors.affiliation: 1Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital of Philadelphia, Philadelphia, PA; 2Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA; 3Arnold School of Public Health, Department of Exercise Science, University of South Carolina, Columbia, SC; 4School of Social and Community Medicine, University of Bristol, Bristol, UNITED KINGDOM; 5Centre of Research in Childhood Health, University of Southern Denmark, Odense, DENMARK; 6Exercise and Health Laboratory, Faculty of Human Movement, Technical University of Lisbon, Lisbon, PORTUGAL; 7Department of Sports Medicine, Norwegian School of Sport Sciences, Oslo, NORWAY; and 8Centre for Exercise, Nutrition and Health Sciences, University of Bristol, Bristol, UNITED KINGDOM.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Mitchell
authors.forename: Marsha
authors.initials: M
authors.lastname: Dowda
authors.forename: Russell R
authors.initials: RR
authors.lastname: Pate
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Kordas
authors.forename: Karsten
authors.initials: K
authors.lastname: Froberg
authors.forename: Luís B
authors.initials: LB
authors.lastname: Sardinha
authors.forename: Elin
authors.initials: E
authors.lastname: Kolle
authors.forename: Angela
authors.initials: A
authors.lastname: Page
mesh_terms: D061725:Accelerometry; D000293:Adolescent; D001315:Australia / Q000453:epidemiology; D015992:Body Mass Index; D001938:Brazil / Q000453:epidemiology; D002648:Child; D004734:Energy Metabolism; D005060:Europe / Q000453:epidemiology; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D063766:Pediatric Obesity / Q000453:epidemiology* / Q000517:prevention & control; D015995:Prevalence; D012044:Regression Analysis; D057185:Sedentary Behavior; D013690:Television; D014481:United States / Q000453:epidemiology; D055105:Waist Circumference