Pediatric studies showed that aerobic exercise reduces metabolic risk, but dose response information is not available.
Test the effect of aerobic training dose on insulin resistance, fatness, visceral fat, and fitness in overweight, sedentary children, and test moderation by sex and race.
Design, Setting, and Participants
Randomized, controlled, efficacy trial from 2003 through 2007, in which 222 overweight or obese, sedentary children (mean age, 9.4 yrs; 42% male, 58% black) were recruited from 15 public schools in the Augusta, GA area.
Low-dose (20 min/d, n = 71) or high-dose (40 min/d, n = 73) aerobic training (13 ± 1.6 wk, 5 d/wk), or control condition (usual physical activity, n = 78); 94% retention.
Main outcome measures
Prespecified primary outcomes were type 2 diabetes risk at posttest, assessed by insulin area under the curve (AUC) from oral glucose tolerance test, aerobic fitness, percent body fat via dual-energy x-ray absorptiometry, and visceral fat via magnetic resonance, analyzed by intent-to-treat.
Most children (85%) were obese. At baseline, the mean BMI was 26 (SD = 4.4). Reductions in insulin AUC were larger in the high-dose (adjusted mean difference [95% CI], −3.56 [−6.26 to −0.85], P = .01) than low-dose group (−2.96 [−5.69 to −0.22], P = .03) ×103 μU/mL) vs control group. Dose-response trends were also observed for body fat (−1.4 [−2.2 to −0.7], P < .001; −0.8 [−1.6 to −0.07] %, P =.03) and visceral fat (−3.9 [−6.0 to −1.7], P < .001; −2.8 [−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 (2.4 [0.4 to 4.5], P =.02; 2.4 [0.3 to 4.5] mL/kg/min, P = .03). High- vs. low-dose group effects were similar for these outcomes. There was no moderation by sex or race.
Three months of 20 or 40 min/d aerobic training improved fitness, and demonstrated dose-response benefits on insulin resistance, general and visceral adiposity in sedentary, overweight or obese children, regardless of sex or race.
Clinicaltrials.gov identifier: NCT00108901