Whether young adults are normal weight or overweight, better fitness is just as strongly linked to thinner artery walls — meaning being fit helps your arteries even if you carry extra weight.

Young adults who can run 3000 meters faster tend to have thinner artery walls in their necks, which is a sign of less early artery damage, even if they’re overweight or have other risk factors.

In young men, being fitter and having lower triglycerides both link to healthier arteries, but in young women, only fitness matters — triglycerides don’t seem to affect artery thickness in this group.

Even though belly fat is often blamed for heart problems, in young, active adults, it doesn’t seem to directly affect artery thickness — fitness and triglycerides matter more.

In older adults with heart disease risk factors, how much they exercise, smoke, or their education level matters more for artery health than how much saturated fat they eat.

No common gene differences found in this group of older adults make them more or less sensitive to the effects of eating saturated fat on their artery thickness.