"I work like a dog to look like this. There's no easy option. I'm obsessed with my health. I love my life and want to live as long as I possibly can so I do whatever it takes. I eat right, I exercise, I'm a total fanatic and pretty much a germo-phobe," the Daily Star quoted Stewart as telling the Daily Mirror.
Stewart, 65, who had previously fought with throat cancer, regularly plays in an over-50s football team in California in a bid to stay healthy. Determined to live long, he follows a strict eating and fitness regime to prevent any heart issues.
"The one thing that absolutely terrifies me is getting sick so I do everything I can to eliminate that... I've been on a team all my life. I play now in an over-50s veterans' league. We have 30 players so you're on for one half and then off, but it's still 45 minutes of running around a pitch," he said.
"I also have a trainer five days a week. I do an hour or two hours a day, a lot of cardio to clear out the arteries. I'm Scottish and we have a history of heart problems in the family. It's all about cleaning out the fat on the inside," Stewart added.