Story Source: PracticeUpdate.com
RESEARCH · September 22, 2014
TAKE-HOME MESSAGE
- This randomized clinical trial assessed the effects of various exercise modalities in obese adolescents. For 22 weeks, 304 participants underwent aerobic training, resistance training, combined aerobic and resistance training, or no exercise. Groups undergoing exercise showed a significantly greater decrease in percentage body fat compared with the no-exercise control, as measured by MRI at baseline and 6 months. However, there was no significant difference in this outcome between the combined training group and those undergoing aerobic or resistance training alone. Changes in waist circumference of −0.2 cm, −3.0 cm, −2.2 cm, and −4.1 cm were observed for the no-exercise, aerobic, resistance, and combined training programs, respectively.
- Both total body fat percentage and waist circumference were significantly decreased in obese adolescents who exercised compared with no-exercise controls. While not significantly different in this study, with greater adherence, combined training may prove more effective than aerobic or resistance training alone.
Expert Comment
Cardiology
Paul D Thompson MD
The Healthy Eating Aerobic and Exercise Training in Youth (HEARTY) clinical trial randomized 304 obese adolescents aged 14 to 18 years to aerobic exercise training (AT), resistance exercise training (RT), combined AT and RT (CT), or non-exercise control (CO) groups. Participants entered a 16-session pre-randomization exercise training (ET) program and had to attend 13 of the sessions to be randomized. ET after randomization was performed four times weekly for 6 months at increasing intensity and training load. Exercise trainers supervised two sessions weekly for the first 3 months and one session weekly for the last 3 months. All participants received dietary counseling at baseline and at 3 and 6 months.
The percent body fat (%BF) decreased only slightly in all groups: 0.3% in CO, 1.1% in AT, 1.6% in RT, and 1.4% in CT. Absolute body fat decreased 1.2 kg with AT, 1.3 kg with RT, and 1.7 kg with CT, but lean body mass increased 0.7, 1.4, and 0.8 kg, respectively, in the same groups, so that the absolute change in body weight was discouragingly small. The median attendance at the ET sessions was only 62%. The authors emphasized that, among those attending ≥70% of sessions, the reductions in %BF were 2.4% for CT, 1.2% for AT, and 1.6% for RT, and the %BF loss with CT was significantly greater than that for AT; however, this seems to be a small victory.
The issue is that the changes in body fat and body weight with 6 months of exercise training were small, even among the good adherers. This reinforces the old adage that exercise is primarily useful to help maintain weight reduction, but that dietary restrictions plus or minus exercise are required to achieve the weight loss in the first place.
ABSTRACT
IMPORTANCE
Little evidence exists on which exercise modality is optimal for obese adolescents.
OBJECTIVE
To determine the effects of aerobic training, resistance training, and combined training on percentage body fat in overweight and obese adolescents.
DESIGN, SETTING, AND PARTICIPANTS
Randomized, parallel-group clinical trial at community-based exercise facilities in Ottawa (Ontario) and Gatineau (Quebec), Canada, among previously inactive postpubertal adolescents aged 14 to 18 years (Tanner stage IV or V) with body mass index at or above the 95th percentile for age and sex or at or above the 85th percentile plus an additional diabetes mellitus or cardiovascular risk factor.
INTERVENTIONS
After a 4-week run-in period, 304 participants were randomized to the following 4 groups for 22 weeks: aerobic training (n = 75), resistance training (n = 78), combined aerobic and resistance training (n = 75), or nonexercising control (n = 76). All participants received dietary counseling, with a daily energy deficit of 250 kcal.
MAIN OUTCOMES AND MEASURES
The primary outcome was percentage body fat measured by magnetic resonance imaging at baseline and 6 months. We hypothesized that aerobic training and resistance training would each yield greater decreases than the control and that combined training would cause greater decreases than aerobic or resistance training alone.
RESULTS
Decreases in percentage body fat were −0.3 (95% CI, −0.9 to 0.3) in the control group, −1.1 (95% CI, −1.7 to −0.5) in the aerobic training group (P = .06 vs controls), and −1.6 (95% CI, −2.2 to −1.0) in the resistance training group (P = .002 vs controls). The −1.4 (95% CI, −2.0 to −0.8) decrease in the combined training group did not differ significantly from that in the aerobic or resistance training group. Waist circumference changes were −0.2 (95% CI, −1.7 to 1.2) cm in the control group, −3.0 (95% CI, −4.4 to −1.6) cm in the aerobic group (P = .006 vs controls), −2.2 (95% CI −3.7 to −0.8) cm in the resistance training group (P = .048 vs controls), and −4.1 (95% CI, −5.5 to −2.7) cm in the combined training group. In per-protocol analyses (≥70% adherence), the combined training group had greater changes in percentage body fat (−2.4, 95% CI, −3.2 to −1.6) vs the aerobic group (−1.2; 95% CI, −2.0 to −0.5; P = .04 vs the combined group) but not the resistance group (−1.6; 95% CI, −2.5 to −0.8).
CONCLUSIONS AND RELEVANCE
Aerobic, resistance, and combined training reduced total body fat and waist circumference in obese adolescents. In more adherent participants, combined training may cause greater decreases than aerobic or resistance training alone.
JAMA Pediatrics
Effects of Aerobic Training, Resistance Training, or Both on Percentage Body Fat and Cardiometabolic Risk Markers in Obese Adolescents: The Healthy Eating Aerobic and Resistance Training in Youth Randomized Clinical Trial