In teen boys, short bursts of intense exercise mainly lower free fatty acids in the blood, while steady, moderate exercise changes more types of fats—including sphingolipids and...

In teen boys who are healthy, doing six weeks of regular cardio or short, intense sprints improves their fitness, but doesn't change their standard cholesterol numbers—meaning those blood tests might miss some of the good changes exercise is doing inside their bodies.

Doing short, intense sprints for six weeks might lower certain types of fats in the blood of healthy teenage boys, which could mean their bodies are using fat differently in a way that's good for their health.

After tough workouts like HIIT or circuit training, fit guys burn fat faster in the hour after exercise compared to easier, steady workouts—even though they burn less fat during the actual workout.

Men who regularly train for endurance sports show greater fat breakdown in abdominal fat tissue during moderate cycling than untrained men, measured by higher glycerol levels, even when hormone levels like adrenaline and insulin are similar.

Doing moderate cardio for six weeks changes certain fat levels in the blood of healthy teenage boys in ways that might help their metabolism work better.