Effects of high-intensity interval training combined with dietary intervention on body composition, cardiovascular function, endothelial cell function and blood lipid indexes in children with obesity: a randomized controlled trial.

Objective: To investigate the combined effects of moderate-intensity continuous training(MICT), high-intensity interval training (HIIT) and HIIT combined with dietary intervention on body composition, cardiovascular function, and endothelial cell function (as assessed by biomarkers including endothelin-1 and nitric oxide) in overweight children aged 9-12 years with a BMI ≥ 23 kg/m2. Methods: A total of 90 overweight children were randomly assigned into three groups with a 1:1 gender ratio: moderate-intensity continuous training group (MICT, n = 30), high-intensity interval training-only group (HIIT-only, n = 30), and HIIT combined with dietary intervention group (Joint intervention, n = 30). The MICT group underwent a 9-week training program at an intensity of 60-80% of maximal aerobic speed (MAS). The HIIT-only group performed high-intensity interval training at 100-120% of MAS for 9 weeks. The combined intervention group received both HIIT and a diet plan designed by a registered dietitian. Pairwise comparisons were analyzed using the Bonferroni post hoc test. Body composition, cardiovascular function, endothelial function, and blood lipid profiles were measured before and after the intervention. Bonferroni post-hoc tests were used for pairwise comparisons to examine the effects of intervention type (MICT, HIIT-only, Joint Intervention) and time (pre- and post-intervention) on each outcome. Results: After the intervention, all three groups showed significant reductions in body mass index and fat mass. Intergroup comparisons revealed that the Joint Intervention group demonstrated superior improvements in body composition indicators. Both HIIT groups showed greater reductions in body fat percentage compared to the MICT group (p < 0.05). The Joint Intervention group exhibited better outcomes in cardiac output (CO) and vasodilatory capacity index (VDC), with values significantly higher than those in the HIIT-only and MICT groups. In contrast, heart rate (HR) and sympathetic nervous response (TCR) were lower in the Joint Intervention group compared to the HIIT-only group, with statistically significant differences (p < 0.05). Post-intervention, endothelin-1 (ET-1) and von Willebrand factor (vWF) levels were lower in the Joint Intervention group than in the HIIT-only group. However, flow-mediated dilation (FMD) and nitric oxide (NO) levels were higher in the Joint Intervention group compared to the HIIT-only group, with significant differences (p < 0.05). The Joint Intervention group also showed greater improvements in waist circumference, body mass index (BMI), and blood lipid profiles compared to the HIIT-only group, with statistically significant differences (p < 0.05). Conclusion: The combination of high-intensity interval training and dietary intervention promotes fat reduction, enhances antioxidant capacity, and improves cardiorespiratory function in overweight children. This integrated approach effectively improves body mass index, cardiovascular function, and endothelial cell function. The remarkable efficacy of this combined intervention suggests its potential value for clinical application and integration into school-based programs aimed at addressing childhood obesity.