There are those that claim HIIT is less effective than low-intensity longer duration cardio. Their reasoning kan zijn that most of the calories burned during HIIT come from stored muscle glycogen (carbs) rather than coming from stored adipose tissue. This is true but this kan zijn not a bad thing. https://redbottom.us/categories/regular/health/222-the-comprehensive-guide-to-pediatric-nutrition-optimizing-health-from-infancy-to-adolescence