Effect of exercise intensity and diet intervention on cardiac function among obese children and adolescents

Introduction: Childhood obesity is an important risk factor for the early cardiovascular disease. Studies show conflicting results on whether it is the diet or physical inactivity that play the most important role in treating childhood obesity and possible health consequences. Objectives: The aim of the study was to measure the cardiac function before and after three months intervention including only diet, continuous moderate exercise (CME) and high intensity aerobic interval training (AIT) in obese children/adolescents; to compare the cardiac function among exercise (CME+AIT) combined diet intervention with diet intervention only. Method: A randomized controlled trial study was performed. In total 29 obese (ISO-BMI ≥30 kg/m2) children (16 girls, 13 boys) with mean age 11.3 ± 2.4 years and ISO-BMI 32.9 ± 3.3 kg/m2 were randomized to either of three months intervention groups: Diet (32.8 ± 3.1 kg/m2), CME (34.8 ± 4.3 kg/m2) and AIT (31.2 .± 2.2 kg/m2) respectively. The CME performed training at 70% of maximal heart rate (HRmax) for 47 minutes and the AIT performed 4×4 minutes training at 85-95% of HRmax with 3 minutes active interval (60% HRmax) in between. Both intervention groups performed the training session twice in the lab and once at home in each week for consecutive 12 weeks. Diet intervention together with AIT and CME were counseled together with their caregiver for healthy food choices for every second weeks for consecutive three months of intervention period. Anthropometric measurement with body composition, maximal oxygen uptake and resting echocardiography were done before and after intervention program. Mean ± standard deviation was calculated. Paired t-test and one way ANOVA test was used to compare the mean differences within and between the groups from baseline to three months test. The statistical significance of p< 0.05 was set. Result: In total 21 subjects completed the three months intervention. BMI tended to reduce in all three groups. Left ventricular end-diastolic volume indexed to body surface area (LVEDVI) increased almost significantly in the CME group by 24.5% (p=0.09) and AIT group by 30.5% (p=0.2) respectively. Ejection fraction increased significantly in the AIT by 16.3% (p=0.05). The CME improved lean body mass (LBM) (p=0.04) significantly as well as AIT improved LBM almost significantly (p=0.07). The resting heart rate significantly reduced by 10 BPM (p=0.05) and the upright blood pressure had a tendency towards reduction by 6 mmHg (p=0.21). Maximal oxygen uptake did not improve after intervention. When exercise (CME+AIT) combined diet intervention was compared with diet intervention only, exercise combined diet intervention improved LVEDV by 24.6% (p=0.02) and LVEDVI by 26.9% (p=0.03) and almost significantly shortened IVRT (p=0.08); diet intervention reduced IVRT (p=0.006) after intervention. LBM significantly improved among exercise combined diet intervention by 1.7% (p= 0.003). The other variables remained unchanged in both groups after intervention. Conclusion: Aerobic interval training combined with diet advice improved cardiac function more than moderate exercise and only diet intervention. The exercise intervention (CME+AIT) improved more variables than the diet intervention alone. Limitation and strength: Significant difference was not achieved in several parameters due to small sample size. However the safe, well-controlled and highly defined exercise intensity intervention regimen is a strength of this study