Millennials may think they have an infinite amount of time to work off those greasy hamburgers and salty French fries before they hit middle age. But that is proving untrue. University of Maryland School of Medicine researchers found that a high cholesterol level in your teens and early 20s can be predictive of heart attack or stroke later in life – even if individuals gets their cholesterol numbers under control by their 30s.

The researchers followed some 5,000 people aged 18 to 30 years, as they grew older. During the course of the study, 275 of those subjects had a cardiovascular event, like a stroke or heart attack. Significantly, those patients were more likely to have had high cholesterol, including a high LDL, “bad” cholesterol, when they were younger.

The results showed that if two persons are both aged 40 and have the same LDL levels, the person with higher cholesterol as a teenager is at greater risk for heart attack or stroke. This is a new finding.

The American Heart Association explains that cholesterol is the waxy stuff in the bloodstream that is both good for you and bad for you. The body can make its own cholesterol, but a lot of it comes from eating animal products like eggs, yogurt, steak and pork chops. Cholesterol forms a structural part of the body’s cells, so some of it is necessary, but too much is dangerous — this why there are the terms “good” and “bad” cholesterol.

LDL can stick to artery walls, like traffic piling up on the sides of the road. But where a traffic pileup just slows down commuters, blocked arteries can cause strokes and heart attacks.

For those of any age with high cholesterol, treatment is a priority. There are literal and figurative steps people with high cholesterol can take. A better diet and more exercise, even walking, can lower LDL. Prescription drugs can also lower high cholesterol.

Even if they feel great, younger people should keep just as close an eye on their cholesterol as people who are older. Finding problems early could save lives down the road.