Obese adolescents who participated in aerobic, resistance or combined exercise decreased their total body fat and waist circumference, according to study findings in JAMA Pediatrics.
Ronald J. Sigal, MD, MPH, of the University of Calgary in Alberta, and colleagues randomly assigned 304 previously inactive children to participate in aerobic training, resistance training or combined aerobic and resistance training for 22 weeks. Study participants were aged 14 to 18 years and had a BMI at or above the 95th percentile for age and sex or at or above the 85th percentile plus diabetes or a cardiovascular risk factor. Before participating in training interventions, children completed a run-in period in which they performed 15 to 30 minutes of aerobic exercise at 65% of measured maximum heart rate and seven resistance exercises four times a week for 4 weeks.
Ronald J. Sigal
All study participants were counseled by a dietitian at baseline, 3 and 6 months to promote healthy eating with a daily energy deficit of 250 kcal. The three exercise intervention groups were asked to attend gymnasiums four times a week. Exercise training progressed in duration and intensity over time. The aerobic group (n=75) exercised on treadmills, elliptical machines or bicycle ergometers. The resistance group (n=78) completed seven exercises using weight machines or free weights. The combined exercise group (n=75) completed the full aerobic and resistance training programs during each session. Seventy-six children served as the non-exercising control group.
Median exercise training adherence from baseline to 26 weeks was 62% in the aerobic group, 56% in the resistance group and 64% in the combined group. Seventy-five participants withdrew between randomization and 6 months.
Percentage body fat decreased in all exercising groups, by –1.1 in the aerobic group, –1.6 in the resistance group and –1.4 in the combined group vs. –0.3 in the control group. In per-protocol analysis, in which exercise training adherence was 70% or more, percentage body fat decreased by –2.4 in the combined group, –1.2 in the aerobic group and –1.6 in the resistance group.
Children in the aerobic group experienced a decrease in waist circumference of –3 vs. –2.2 in the resistance group, –4.1 in the combined group and –0.2 in the control group.
Children in all three exercise groups increased their treadmill time over time.
Children in the aerobic group and resistance group had greater increases in leg press compared with the control group. The resistance group had greater increases in bench press compared with the control group. Children in the combined group had greater increases in leg press, bench press and seated row machines vs. the aerobic group. Muscular strength changes did not differ between the combined group and resistance group regarding leg press, bench press and seated row machines.
“The HEARTY trial showed that aerobic training, resistance training, and their combination decreased body fat percentage in obese adolescents,” the researchers wrote. “Adolescents who want to maximize the effect of exercise on these variables should ideally perform both aerobic and resistance exercise, but significant benefit can be achieved through either type of exercise alone.”
Disclosure: The researchers report no relevant financial disclosures.