The review found no statistically significant advantage for high-intensity interval training, often called HIIT, over continuous aerobic training in body weight, body mass index or body fat percentage among youth with overweight or obesity. It also stated that the evidence did not establish equivalence, meaning it did not show that the two approaches produce the same results.
What was compared
The comparison was between interval protocols such as cycling sprints, treadmill intervals, intermittent running and repeated high-intensity walking, and continuous activities such as cycling, treadmill exercise, running or other endurance training. The programs lasted three to 16 weeks and were delivered two to 10 times a week.
Eligibility required randomized controlled trials in participants aged 6 to 19 with overweight or obesity, a direct interval-versus-continuous comparison and at least one of the target outcomes. Searches covered PubMed, Embase, Web of Science, CNKI, Wanfang and VIP from database inception through December 31, 2024. The review reported its identification, screening, eligibility and inclusion procedures according to PRISMA 2020.
Fourteen independent randomized trials were included. Outcome-specific analyses included 409 participants for body weight, 432 for BMI and 331 for body fat percentage, and reported ages were approximately 7 to 19 years.
The pooled results were close
For body weight, 13 trials involving 409 participants produced a pooled estimate of 0.37 kilograms lower with interval training than with continuous exercise. The 95% confidence interval ran from 0.89 kilograms lower to 0.15 kilograms higher, and the result was not statistically significant, with P = 0.146.
Body mass index, or BMI, also favored interval training in the point estimate, but the result was not statistically significant. Across 14 trials involving 432 participants, the pooled difference was 0.14 kilograms per square metre lower, with a 95% confidence interval from 0.31 lower to 0.02 higher and P = 0.089.
Body fat percentage also showed no statistically significant difference. In 11 trials involving 331 participants, the pooled estimate was 0.33 percentage points lower with interval training, but the 95% confidence interval extended from 1.33 points lower to 0.67 points higher, with P = 0.481. Results varied more across these studies than they did for weight or BMI, with I-squared at 60.3%.
These pooled results were calculated as mean differences using random-effects models, with 95% confidence intervals. The review assessed between-study variation with Q, tau-squared and I-squared statistics, and treated two-sided P values below 0.05 as statistically significant.
The evidence had important limits
Several checks left the main conclusion intact. Leave-one-out analyses did not materially alter the estimates. When reconstructed results from one study were excluded, the body-weight difference was 0.36 kilograms lower and the BMI difference was 0.21 kilograms per square metre lower, but both confidence intervals still included zero; including a study with unclear allocation also left the estimates non-significant.
Egger tests did not detect statistically significant small-study effects for body weight, BMI or body fat percentage. But the tests were based on only 11 to 14 trials per outcome, which makes the finding less conclusive.
Subgroup tests found no statistically significant modification by weekly frequency, intervention duration or mean age. The subgroup with at least four sessions a week for body fat contained just one trial, and the age-category interaction had P = 0.067. A separate, exploratory study-level meta-regression found that older mean age was associated with a more HIIT-favorable body-fat estimate. The coefficient was minus 0.449 percentage points per year, with a 95% confidence interval from minus 0.872 to minus 0.026 and P = 0.040.
The review's risk-of-bias assessment also called for caution. Only one of the 14 trials, or 7.1%, was judged at low overall risk of bias; 13 trials, or 92.9%, raised some concerns, and none was rated high risk. Incomplete reporting of randomization was the most frequent concern, followed by missing outcome data in six trials, or 42.9%.
A narrow conclusion
Taken together, these findings leave no demonstrated winner between the two exercise formats for the three body-composition outcomes measured. They also do not show that HIIT and continuous aerobic training are equivalent. The result is a narrower conclusion: neither format had a statistically significant advantage in this review, and the evidence did not settle whether their effects are the same.
The authors declared that they received no financial support for the work or its publication.
Paper data and sources
Original title: Effects of high-intensity interval training versus continuous aerobic training on body weight, body mass index, and body fat percentage in youth with overweight or obesity: a systematic review and meta-analysis
Authors: Jin Y, Zhou Y, Zhang H
Journal/Repository: Frontiers in pediatrics
Status: Peer-reviewed
First online: 2026-10-10
DOI: Not available
Original paper · Full text