About three years after winning season 8 of “The Biggest Loser,” Danny Cahill started sustaining injuries from working out so much.

“It became really evident that my body was really tired, and my joints were breaking down,” the 56-year-old from Broken Arrow, Oklahoma, tells TODAY.com. “I would have injury after injury, and I couldn’t keep it up.”

The Biggest Loser aired for 17 seasons from 2004 until 2016 on NBC, which is owned by NBC Universal, TODAY’s parent company. Those who lost the highest percentage of weight competed for prizes, including $250,000 and the title of “the biggest loser” for the winner.

After Cahill’s win in 2009 because he shed 239 pounds in six months, three weeks and five days, he returned home and added as much movement as he could into his daily routine.

“I exercised every time I got a chance. If I went and got a haircut across town, I would ride my bike,” he says, adding it was an 18-mile trip one way. “I would walk everywhere I went that I could. I would jog to the post office to check the P.O. box. I incorporated working out into my life.”

Danny Cahill after being on "The Biggest Loser."Danny Cahill after winning “The Biggest Loser.”Trae Patton/NBCU Photo Bank / Getty Images

He ran two marathons and “felt like a million bucks,” he recalls. His doctor weaned him off medications.

“(My doctor) was blown away,” Cahill says. “I came back 240 pounds lighter, and my numbers were good. I was pulled off my meds because my blood pressure fell in line.”

While his doctor was pleasantly surprised by Cahill’s success, he did worry about the speed at which Cahill lost the weight. Still, Cahill felt amazing.

“Everything was just great,” he says. “It was the weight that was causing all these (health) issues.”

But then the injuries began. He recalls being on an obstacle course and injuring a ligament in his big toe from hoisting himself up onto a platform.

“It almost tore (the ligament) in my big toe,” Cahill says. “I couldn’t walk. I wouldn’t wear a shoe on that foot for a month.”

At the time, he walked, biked and ran most of the time for his exercise. To heal, he stopped working out to rest and noticed that he gained 20-30 pounds. Even that slight gain made Cahill feel bad.

“You start feeling this pressure and this shame,” he says. “When I started regaining the weight, I withdrew.”

Cahill shares his experience with “The Biggest Loser” in the Netflix documentary “Fit for TV: The Reality of The Biggest Loser.” In the three-part series, he reveals that he gained back all the weight he lost. It became increasingly difficult to incorporate so much exercise into his busy life with a full time career and parenting.

These days, “my movement is not very often because by the time I get home from a day of work, I’m exhausted,” Cahill says.

Cahill also faced some health troubles. Two years ago, he felt a pain in his back and visited the emergency room. He waited for 20 hours and considered leaving a few times. But something kept him there.

“I started feeling really strange, and then I was like something’s wrong here,” he says. “If you feel like something’s wrong — they always say that people have this sense of dread or a sense that says something’s wrong — get it checked out.”

Doctors found a large aneurysm, which they attributed to a failing heart valve, which was “partially fused” since he was born.

“I was lucky to find (the aneurysm),” he says. “I could be dead right now.”

Doctors repaired his valve during open heart surgery and he has been doing well since. He takes blood pressure medication and prescription for nerve damage in his foot, which makes it hard for him to walk at times.

Cahill and his wife recently made some lifestyle changes.

“We’re taking walks with the dogs. We are starting to cook better and eat whole foods instead of processed foods,” Cahill says. “That’s going to make a difference. It just takes time to see that difference.”

He hopes he’ll be able to stop taking blood pressure medication again.

“I’ve gotten to where I can walk pretty good distances again and I’m happy about that,” he says. “I can’t wait for it to be six months, a year, for me to be off those meds. That’s my goal.”

Even knowing what he knows now about “The Biggest Loser,” Cahill says he would do it again.

“It was a lot of fun. It was very scary. It was very exhilarating. It was boring at times,” he says. “If I did it again now, I would do it a little different. I would eat some more because I don’t know that eating an extra 400 or 500 calories a day would have made that much of a difference in my weight loss as hard as we were working out.”

He says that because he felt motivated to win, he sometimes ate fewer calories than the calories recommended by the show doctor, Dr. Robert Huizenga.

Cahill feels proud of what he accomplished on the show.

“I still have records on ‘The Biggest Loser’ of the highest percentage of weight loss of any man, of losing double digits every week for seven weeks in a row, which is a record that still stands with 380-plus contestants in America,” he says.

He remembers watching the finale with his son, David, who felt surprised by how much weight his dad lost.

“What I want everybody that hears this, including my kids and everyone around me, is that you can do anything if you put your mind to it,” he says. “If you have the support system around you … you can do anything.”