Brief periods of exercise yields substantial benefits in obese children

Exercise Dose and Diabetes Risk in Overweight and Obese ChildrenA Randomized Controlled Trial

Catherine L. Davis, PhD; Norman K. Pollock, PhD; Jennifer L. Waller, PhD; Jerry D. Allison, PhD; B. Adam Dennis, MD; Reda Bassali, MD; Agustín Meléndez, PhD; Colleen A. Boyle, PhD; Barbara A. Gower, PhD

[+] Author Affiliations

JAMA. 2012;308(11):1103-1112. doi:10.1001/2012.jama.10762.

ABSTRACT 

Context  Pediatric studies have shown that aerobic exercise reduces metabolic risk, but dose-response information is not available.

Objectives  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.

Design, Setting, and Participants  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.

Intervention  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).

Main Outcome Measures  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 [[Vdot]O₂]), 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] × 10³ μU/mL; P = .01) and the low-dose group (adjusted mean difference, −2.96 [95% CI, −5.69 to −0.22] × 10³ 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 [Vdot]O₂, 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.

Conclusion  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.

COMMENT: Another encouraging study demonstrating that brief regular doses of exercise can have substantial and impressive beneficial effects.  This time this was demonstrated on our most vulnerable populations, obese children.  Additionally there seemed to be no racial or sex differences in its effectiveness.  Given the recent post on 80-year-old, we can see that brief, sustained exercise can be beneficial at any age..