Effects of school-based high-intensity interval training on body composition, cardiorespiratory fitness and cardiometabolic markers in adolescent boys with obesity: a randomized controlled trial.

Researchers in a school setting gave 45 boys aged 10 to 13 with obesity one of three options over 12 weeks: high-intensity interval training (short bursts of hard running mixed with recovery jogs), moderate-intensity continuous training (steady-paced running), or no structured exercise. Both training groups lost similar amounts of weight and body fat, but the high-intensity group saw a notably larger increase in aerobic fitness—about 60% more improvement than the moderate-intensity group. The high-intensity group also showed a sharper drop in visceral fat (the fat around internal organs) and was the only one to lower their LDL cholesterol.

Both groups improved their insulin resistance markers equally. The findings suggest that short, intense running sessions in a school setting can produce real metabolic and fitness changes in this age group, though the practical advantages of choosing one approach over the other remain somewhat unclear.

This study looked at whether short bursts of very intense exercise could help young people with obesity feel fitter and healthier. Researchers compared two types of running workouts over three months: one group did short, hard sprints with recovery breaks, and another did longer, steady-paced runs.

Both groups ended up losing a similar amount of weight and body fat. The main difference was that the group doing the short, hard bursts improved their fitness level more noticeably and showed bigger changes in the deeper fat around their organs, plus their cholesterol improved.

Both groups also handled sugar in their blood better after 12 weeks. The study was small and only included boys, so it is not clear yet how these findings might apply more broadly.

What this tells us is that getting active in school using either approach can make a real difference, but more research with larger and more varied groups of young people is needed.

This is a summary of research, not medical advice. Talk to your own healthcare provider about anything affecting your care.

This controlled trial offers a school-based model worth noting for how brief, high-intensity interval training compares to traditional moderate-intensity continuous work in an adolescent obesity population. Both approaches produced equivalent reductions in BMI and fat mass over 12 weeks, suggesting that adherence and total work may matter as much as intensity distribution for body composition.

Where HIIT appeared to have an edge was in cardiorespiratory fitness gains (a 6.1 mL/kg/min improvement versus 3.8 for MICT) and visceral adipose reduction, which aligns with the metabolic signature often associated with higher-intensity work. The finding that LDL cholesterol dropped only in the HIIT group is interesting but single-outcome focused, and both groups achieved similar improvements in insulin resistance, so cardiometabolic benefits were not cleanly separated.

The sample was small (15 per group) and limited to boys aged 10 to 13 in a single school context, which constrains generalizability. The work suggests HIIT may offer some physiological advantages in this age group, but the practical significance of those differences and whether they translate to better long-term health outcomes remain open questions.