Last February, “The Biggest Loser” host Bob Harper set out to his New York gym for a routine Sunday morning workout. It seemed like just another day in the fitness expert’s life.

But midway through the workout, Harper suddenly found himself needing to stop. He laid down and rolled on to his back.

“I went into full cardiac arrest. I had a heart attack.”

While Harper doesn’t recall very much from that day, he was told that a doctor who happened to be in the gym was able to act quickly and perform CPR on him. The gym was equipped with an automated external defibrillator (AED), so the doctor used that to shock Harper’s heart back into a regular beat until an ambulance arrived.

The chances of him surviving? A slim six percent.

He woke up two days later to the shocking news that he had nearly died. He credits his friend who had been working out with him, along with the gym coach, and doctor, for his survival.

Leading up to his heart attack, Harper says he hadn’t experienced any of the common warning signs, such as chest pain, numbness, or headaches, though he did feel dizzy at times. “About six weeks prior to my heart attack, I actually fainted in the gym. So there were definitely signs that something was wrong, but I chose not to listen,” he says.

Warren Wexelman, a cardiologist with the NYU Langone School of Medicine and Medical Center, says Harper probably missed other warning signs because of his peak physical condition. “The fact that Bob was in such amazing physical condition before his heart attack was probably the reason he didn’t sense all the chest pain and shortness of breath that someone in not as great physical condition would have felt.”

“Honestly, if Bob wasn’t in the condition that Bob was in, he probably never would have survived.”

So how did a 51-year-old man in such great condition have a heart attack in the first place?

A blocked artery, Wexelman explains, as well as the discovery that Harper carries a protein called lipoprotein(a), or Lp(a). This protein increases the risk of heart attack, stroke, and valve blockages. Harper most likely inherited it from his mother and maternal grandfather, who both died from heart attacks at 70 years old.

But while carrying Lp(a) certainly increases one’s risk, many other factors go into increasing one’s risk for a heart attack. “There’s never just one risk factor for heart disease, it’s multiple things,” says Wexelman. “Family history, genetics you inherit, diabetes, high cholesterol, and high blood pressure all come together to make the picture of what we call heart disease, and makes the person — no matter if they are in the best shape, or worst shape — much more prone to having one of these events.”

Harper has made it his mission to address every underlying issue — from diet to routine.

Rather than approach each lifestyle change as a violation of his already healthful approach to fitness and wellness, he’s choosing to embrace the changes he has to make in order to ensure a positive — and lasting — recovery.

“Why have guilt or shame about something that’s completely out of your control like genetics?” asks Harper. “These are the cards that are dealt and you do the best you can to manage any condition that you have.”

As well as attending cardiac rehab and slowly easing back into exercise, he’s had to radically overhaul his diet. Before the heart attack, Harper was on a Paleo diet, which involves eating mostly high-protein, high-fat foods.

“What I realized after my heart attack was that my diet was lacking balance and that’s why I came up with ‘The Super Carb Diet’ book,” he recalls. “It’s about being able to press the reset button and getting all the macronutrients back onto your plate — protein, fat, and carbs.”

Though Harper tackled recovery — and the requisite changes to his lifestyle — with gusto, he admits that he was startled when he learned that having one heart attack puts you at increased risk for a repeat heart attack.

Indeed, according to the American Heart Association, 20 percent of heart attack survivors over age 45 experience a repeat heart attack within five years. And of the 790,000 heart attacks experienced in the United States each year, 210,000 of those are repeat heart attacks.

Learning this reality only further emboldened Harper to take control of his body. “It was in that moment that I realized I was going to do everything and anything that my doctors told me,” he says.

One of those doctor’s suggestions was taking the medication Brilinta. Wexelman says the drug stops the arteries from reclogging and reduces chances of future heart attacks.

“We know that Brilinta is not a drug that anybody can take because it can cause bleeding,” says Wexelman. “The reason that Bob is a good candidate for this drug is because he’s such a good patient and people on these drugs really need to listen to their doctor who’s caring for them.”

While taking Brilinta, Harper decided to team up with the drug’s manufacturer, AstraZeneca, to help launch an education and support campaign for heart attack survivors called Survivors Have Heart. The campaign is an essay competition that will see five heart attack survivors from all over the country attend an event in New York City at the end of February to raise awareness for the warning signs of repeat heart attacks.

“I’ve met so many people since doing this and they all have a special and important story to tell. It’s great to give them an outlet to tell their story,” he says.

As part of the campaign, Harper coined six survivor basics to help other people who have experienced a heart attack face their fears and be proactive with their self-care — by focusing on mindfulness, as well as physical health and treatment.

“This is so personal and so real and organic to me, because I’m contacted by a lot of people who want tips on what to do after suffering a heart attack,” he says. “Survivors Have Heart gives people a place and community to turn to for tips.”

As far as where his story will go from here, Harper says he has no current plans to return to “The Biggest Loser” after 17 seasons. For now, helping others manage their heart health and avoid repeat heart attacks takes priority.

“I feel like my life is taking a turn,” he says. “For now, with Survivors Have Heart, I have a whole other set of eyes that are on me looking for guidance and help, and that’s exactly what I want to be able to do.”

He also plans to advocate the importance of learning CPR and having AEDs available in public places where people congregate. “These things helped save my life — I want the same for others.”

“I went through a major identity crisis this past year of having to discover new outlets in my life, and redefine who I thought I was for these past 51 years. It’s been emotional, difficult, and challenging — but I’m seeing light at the end of the tunnel and feeling better than I have.”