The Effects of High-Intensity Interval Training on Inflammatory Cytokines in Children and Adolescents with Obesity: A Systematic Review and Meta-Analysis

<b>Background</b>: High-intensity interval training (HIT) is a time-efficient strategy to improve metabolic health in children, but its impact on inflammatory markers is still unclear. Therefore, we conducted a meta-analysis to examine the role of HIT on pro-inflammatory cytokines including C-reactive protein (CRP), interleukin 6 (IL-6), and tumor necrosis factor-alpha (TNF-α) in children with overweight/obesity. <b>Methods</b>: A meta-analysis was conducted following PRISMA guidelines. PubMed, Web of Science, Scopus, and Embase were searched up to 31 July 2025, for studies involving children with overweight/obesity aged 6 to 18 years. Randomized controlled trials and non-randomized controlled trials with outcome measurements that included CRP, IL-6, and TNF-α were included. Random-effects models were used to aggregate a mean effect size (ES) with 95% confidence intervals (CI), and potential moderators were explored. <b>Results</b>: In total, 768 participants from 15 studies were included. HIT significantly improved CRP (574 participants, 13 studies, SMD = -0.63, 95% CI: -1.02 to -0.24, <i>p</i> < 0.01) when compared to control group/pre-intervention. There were no significant effects on IL-6 and TNF-α, and no differences when compared to moderate-intensity training. Subgroup analyses indicated greater effectiveness in intervention duration, work-and-rest ratio, and work time were the significant moderators (<i>p</i> < 0.05). <b>Conclusions</b>: High-intensity interval training is effective for reducing CRP levels in children with obesity. Intervention duration, work-and-rest ratio, and work time can affect the intervention effects of HIT.