title: Exercise dose and diabetes risk in overweight and obese children: a randomized controlled trial.
abstract: BACKGROUND
  Pediatric studies have shown that aerobic exercise reduces metabolic risk, but dose-response information is not available.
  
  
  OBJECTIVE
  To test the effect of different doses of aerobic training on insulin resistance, fatness, visceral fat, and fitness in overweight, sedentary children and to test moderation by sex and race.
  
  
  METHODS
  Randomized controlled efficacy trial conducted from 2003 through 2007 in which 222 overweight or obese sedentary children (mean age, 9.4 years; 42% male; 58% black) were recruited from 15 public schools in the Augusta, Georgia, area.
  
  
  METHODS
  Children were randomly assigned to low-dose (20 min/d; n = 71) or high-dose (40 min/d; n = 73) aerobic training (5 d/wk; mean duration, 13 [SD, 1.6] weeks) or a control condition (usual physical activity; n = 78).
  
  
  METHODS
  The prespecified primary outcomes were postintervention type 2 diabetes risk assessed by insulin area under the curve (AUC) from an oral glucose tolerance test, aerobic fitness (peak oxygen consumption [VO2]), percent body fat via dual-energy x-ray absorptiometry, and visceral fat via magnetic resonance, analyzed by intention to treat.
  
  
  RESULTS
  The study had 94% retention (n = 209). Most children (85%) were obese. At baseline, mean body mass index was 26 (SD, 4.4). Reductions in insulin AUC were larger in the high-dose group (adjusted mean difference, -3.56 [95% CI, -6.26 to -0.85] × 10(3) μU/mL; P = .01) and the low-dose group (adjusted mean difference, -2.96 [95% CI, -5.69 to -0.22] × 10(3) μU/mL; P = .03) than the control group. Dose-response trends were also observed for body fat (adjusted mean difference, -1.4% [95% CI, -2.2% to -0.7%]; P < .001 and -0.8% [95% CI, -1.6% to -0.07%]; P = .03) and visceral fat (adjusted mean difference, -3.9 cm3 [95% CI, -6.0 to -1.7 cm3]; P < .001 and -2.8 cm3 [95% CI, -4.9 to -0.6 cm3]; P = .01) in the high- and low-dose vs control groups, respectively. Effects in the high- and low-dose groups vs control were similar for fitness (adjusted mean difference in peak VO2, 2.4 [95% CI, 0.4-4.5] mL/kg/min; P = .02 and 2.4 [95% CI, 0.3-4.5] mL/kg/min; P = .03, respectively). High- vs low-dose group effects were similar for these outcomes. There was no moderation by sex or race.
  
  
  CONCLUSIONS
  In this trial, after 13 weeks, 20 or 40 min/d of aerobic training improved fitness and demonstrated dose-response benefits for insulin resistance and general and visceral adiposity in sedentary overweight or obese children, regardless of sex or race.
  
  
  BACKGROUND
  clinicaltrials.gov Identifier: NCT00108901.
authors.affiliation: Georgia Prevention Center, Institute for Public and Preventive Health, Department of Pediatrics, Medical College of Georgia, 1120 15th St, Ste 1640, Augusta, GA 30912, USA. cadavis@georgiahealth.edu
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Davis
authors.forename: Norman K
authors.initials: NK
authors.lastname: Pollock
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Waller
authors.forename: Jerry D
authors.initials: JD
authors.lastname: Allison
authors.forename: B Adam
authors.initials: BA
authors.lastname: Dennis
authors.forename: Reda
authors.initials: R
authors.lastname: Bassali
authors.forename: Agustín
authors.initials: A
authors.lastname: Meléndez
authors.forename: Colleen A
authors.initials: CA
authors.lastname: Boyle
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Gower
mesh_terms: D050154:Adiposity; D002648:Child; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D050152:Intra-Abdominal Fat; D008297:Male; D009765:Obesity / Q000628:therapy*; D050177:Overweight / Q000628:therapy*; D010809:Physical Fitness; D057185:Sedentary Behavior; D016896:Treatment Outcome