Can a heart attack happen even if you are relatively young and fit? Yes, and genetics can play a role.

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Biggest Loser host and personal trainer Bob Harper is recovering from a heart attack that left him unconscious for two days, People reported today. The fitness celeb reportedly collapsed two weeks ago while working out at the gym, and was recently released from the hospital after an eight-day stay.

But Harper, 51, is hardly your typical heart attack victim: He’s relatively young, he’s super-fit, and he’s built his career on getting people healthy. Although the specifics of his experience haven’t been shared, we do know one thing: It’s an important reminder that even people with no obvious risk factors can still have underlying heart disease or problems.

A person’s heart disease risk is affected by both environment and genetics, explains Pankaj Arora MD, assistant professor of cardiology at the University of Alabama at Birmingham. (Dr. Arora has not treated Harper.) So it’s possible for someone with a family history of heart problems to live an extremely healthy lifestyle—staying active, eating well, not smoking—and still have an elevated risk. In fact, Harper does blame genetics for his recent event, saying his mother died young from a heart attack.

But how much that risk is elevated depends on a lot of different genes, says Dr. Arora, not just one or two—so inherited risk is difficult to test for. It also depends on how a person lives their life. “DNA is not destiny,” he says, referencing a recent New England Journal of Medicine study. “You can lower your risk by staying fit and healthy even if you have bad genes, just as you can raise a low genetic risk by making unhealthy choices.”

One way Dr. Arora determines if his patients might have genetic heart risks is by asking them a question about their family history: “Did your mother have a heart attack before 65 or your father before 55?” If the answer is yes, he asks a second one: “Did the heart attack happen because of their lifestyle choices, or were they living a healthy life and it still happened anyway?”

“If their mother or father was healthy and still had a heart attack, it is conceivable that one can consider genetic testing to determine genetic risk,” he says. Knowing that patients are at high genetic risk for heart problems can allow them to be monitored more closely; they might also be prescribed medications, like statins, to lower their risk.

That being said, there are hundreds of thousands of gene combinations involved in calculating heart disease risk, and screening for them can be complicated and confusing; that’s why it’s not recommended for most people. It's also not generally covered by insurance, and many doctors worry that test results that indicate "bad genes" could cause patients to lose hope about their heart health and give up on healthy behaviors.

Plus, says Dr. Arora, cases of athletes and other young, fit people suffering sudden serious heart problems are still extremely rare—which is why they’re a big deal in the news when they do happen.

It always makes sense to get clearance from your doctor before you start a new exercise routine, says Dr. Arora, and to know your blood pressure and cholesterol levels—especially if you’re over 35, when these invisible risk factors can start to creep up. “If any of these numbers aren’t where they should be, that gives you some knowledge about your risk and what you should be doing about it,” he says.

But the bottom line, he says, is that no one should be discouraged or scared away from exercise and healthy habits when they hear about an incident like this. “Even if you are born with a high genetic risk, your risk of having an event goes down if you keep up a good physical exercise routine,” he says. “Physical exercise, study after study, has shown to improve cardiovascular health and prolong your life, and that has not changed.”