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.

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.

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.

Even people with a large waist size can have normal levels of internal fat: about 1 in 3 men and women in this study had this, showing waist size isn't always a perfect indicator of visceral fat.

Even people with a normal waist size can have too much fat around their organs: about 1 in 4 men and 1 in 12 women in this study had this hidden fat, showing waist size alone isn't always reliable.

Eating a lot of fatty foods like butter and red meat doesn't seem to make the arteries thicken more in older adults at risk for heart disease, once you account for how much they exercise, smoke, or their education level.