Diet, exercise and an incredibly active lifestyle keep AMC's Cameron Mathison camera ready.

It sounds like a joke, but Cameron Mathison isn't joshing when he reveals he was once advised to work on his physique.

This was before he signed on as ALL MY CHILDREN's Ryan, back when the former model landed a role as a buff bodyguard in the disco drama 54. "The director told me that I had to lean-out because I was going to be taking my shirt off in the movie," reports Mathison.

It's not that Mathison, who prospered as a model, was tubby. He merely didn't yet have the chiseled bod that now sends fans into a swoon. "I didn't have any abs showing at all," he describes. "I was kind of smooth. I wasn't fat by any means, I just wasn't super lean."

Mathison needed advice, "I didn't know any way lean-out and I'd been dating this girl, who told me the Atkins diet was a good way to do it. And that's when I got introduced into not monitoring your fat intake, but monitoring you're your carbohydrate intake because that is your fuel source, your primary fuel source."

He tried to popular diet "for about six weeks, which really made me lose a lot of body fat.... I lost 20, 22 pounds."

After that, he stopped following the Atkins plans, but continued to go light on the carbs, a habit he maintains. "It's the easiest way, by far, to monitor the fat levels on your body. It's not easy to eat without carbohydrates, but if you really work hard at it and cut back on the carbs, you can get lean."

The actor also makes it a point to hit the gym regularly. "You have to make it a part of your schedule," he stresses. "It has to become a priority in your schedule, like going to work and picking up groceries."

Once at the gyn, he says, "I work out very, very intensely. A lot of people work out and just go through the motions and think that they're going to see gains by that. It's going to do absolutely nothing if you go to the gym and kind of work out and don't push your body to the limit. I've had people come up to me in the gym and ask me if I'm all right — they think I'm hurting myself," he notes. "The veins are popping out after the set, I drop the weight and I'm collapsing in exhaustion because I really push my body to it's limits."

That includes a slew of athletic pursuits, especially golfing, skiing and traveling on Rollerblades. But like the rest of us, even the fitness junkie slacks off sometimes. "If I have a late night and have a few drinks, it sort of wipes out my motivation for the next day, next day-and-a-half. So, not only have you gone off your system for that day or that night, but it also blows out the next day."

However, Mathison gives himself permission to abandon his regimen every now and then. "Give yourself a cheat day," he advises. "There's nothing wrong with that. You can't be perfect all the time, and you have to know that. When I was really strict with everything, I used to have those nights when I would inhale everything: every sweet, every bag of chips. But I would give myself a cheat day....That way, you reward yourself for doing well."

For anyone looking to shape up, Mathison offers encouragement. "If you've got goals and want to improve yourself... then I think you should put your mind to it. Absolutely anybody can do it, no matter what they think."