Short bursts of hard effort are often promoted as a quicker route to fat loss than steady cardio. In children and teenagers with overweight or obesity, a new meta-analysis of 14 randomised trials found no measurable difference between the two: high-intensity interval training (HIIT) and continuous aerobic training produced similar changes in body weight, BMI and body fat percentage. The review, by researchers in China and Malaysia, was published in Frontiers in Pediatrics on 25 September and indexed in PubMed on 10 October.
What the 14 trials measured
The authors searched six databases, including two Chinese ones, up to 31 December 2024. Of 792 records, 14 randomised trials directly compared interval training with continuous aerobic exercise in young people aged 6 to 19. The interval programmes included cycling sprints, treadmill intervals and intermittent running, and the comparison arms were continuous cycling, treadmill work or running. Programmes ran for 3 to 16 weeks, two to ten times a week, with 12 weeks the most common length. The trials were small: 432 participants across all 14, or about 31 per trial.
For body weight, 13 trials with 409 participants gave a mean difference of 0.37 kg in favour of HIIT, with a 95% confidence interval from 0.89 kg in favour of HIIT to 0.15 kg in favour of continuous training. The plausible range, in other words, is under a kilogram either way. For BMI (14 trials, 432 participants), the difference was 0.14 units, with an interval from 0.31 in favour of HIIT to 0.02 the other way. For body fat percentage (11 trials, 331 participants), it was 0.33 percentage points, from 1.33 in favour of HIIT to 0.67 against, and here the trials disagreed with each other considerably. None of the three differences was statistically significant. Splitting the trials by sessions per week, programme length or average age did not reveal a group in which HIIT did better.
Where this leaves the HIIT question
The finding matches what earlier direct comparisons in this age group suggested, and it narrows a common claim rather than overturning anything. The review measured body composition only. The authors note that earlier work found HIIT produced larger gains in aerobic fitness and blood pressure in some trials. This review did not test those outcomes, so it does not say HIIT offers nothing. It says that, for weight and fat, the two formats came out level across the trials available. The authors conclude that both can be considered within exercise programmes for young people with overweight or obesity, and that neither can be regarded as generally more effective for weight, BMI or body fat.
Exercise trials in children also differ from everyday life: sessions were scheduled and supervised, and several trials paired exercise with dietary advice. Our News section covers other weight-health research as it is published.
Only one of the 14 trials was judged at low risk of bias. The other 13 raised some concerns, mainly over incompletely reported randomisation or missing outcome data. With so few participants, the subgroup analyses had little power, and the authors say evidence on adherence, long-term maintenance and adverse events was sparse. Body fat was measured by different methods across trials, which may explain why those results varied. The search ended in December 2024, so trials published since are not included, and no analysis by sex or pubertal stage was possible. The authors declared no commercial relationships.
Sources: Jin Y, Zhou Y, Zhang H. 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. Frontiers in Pediatrics, 25 September 2026, 14:1678900 (PubMed 42857145).
