TOPLINE:

In children and adolescents with overweight or obesity, adding a supervised high‑intensity interval training (HIIT) programme to a multidisciplinary lifestyle intervention significantly increased moderate‑to‑vigorous physical activity (MVPA) at 3 months, but benefits were not sustained at 12 months. Notably, additional time spent in vigorous PA was inversely correlated with changes in BMI z scores from baseline to 12 months.

METHODOLOGY:

• Researchers in Denmark conducted a secondary analysis of a randomised controlled trial to investigate effects of adding a supervised 3-month HIIT programme to a 12-month multidisciplinary lifestyle intervention on PA behaviour in children and adolescents with overweight or obesity.
• They included 173 children and adolescents with overweight or obesity (BMI > 85th percentile) who were randomly assigned in a 1:1 ratio to receive either a 12-month lifestyle intervention (control group, n = 83) or a 12-month lifestyle intervention plus a 3-month HIIT programme (HIIT group, n = 90).
• PA was measured using thigh-worn waterproof accelerometers for 7 consecutive days at baseline and 3 and 12 months.

TAKEAWAY:

• At 3 months, the HIIT vs control group showed a significant increase in MVPA by 8.3 min/d (P < .01) vs 0.9 min/d (P = .75).
• MVPA returned to baseline levels at 12 months, with no significant difference observed between the two groups.
• Sedentary time increased across both the groups by 17.5 min/d at 3 months and 29.9 min/d at 12 months (P < .05 for both).
• An additional 10 minutes of vigorous PA per day was associated with a reduction in BMI z scores from baseline to 12 months (P < .05).

IN PRACTICE:

"[The study] findings underscore the potential role of integrating vigorous-intensity PA into exercise programs as a central component of obesity treatment for children and adolescents," the authors wrote.

SOURCE:

This study was led by Charlotte Nørkjær Eggertsen, Department of Pediatrics and Adolescent Medicine, Aalborg University Hospital, Aalborg, Denmark. It was published online on December 29, 2025, in the Scandinavian Journal of Medicine & Science in Sports.

LIMITATIONS:

Only 48% of participants had complete accelerometer-measured PA data at all timepoints, raising the risk of bias despite imputation. Accelerometery may have underestimated the level of MVPA during strength-based exercises in the HIIT programme. The use of unpublished cutoff points developed for children and adolescents using thigh‑worn accelerometers restricted direct comparability with other studies.

DISCLOSURES:

This study was supported by Steno Diabetes Center North Denmark, TrygFonden, Danish Regions, A.P. Møller Foundation, Beckett Foundation, Svend Andersen Foundation, and Memorial legatee for Carpenter Jørgen Holm and wife Elisa F. Hansen. The authors declared having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.