Liam Hemsworth's 'Expendables 2' workout

Liam Hemsworth, the Australian actor and Hunger Games costar arrives 10 minutes early for lunch at the Chateau Marmont, where we've scheduled to meet on a gauzy Los Angeles day. We shake hands and the 6'3" actor settles himself unconsciously into a room-facing seat, potential privacy invasions be damned. He's wearing a varicolored sweater with a shawl collar—the cashmere version of Jeff Spicoli's drug rug—and his hair is in a state best described as subdued bed head.

Click here to see Liam Hemsworth's exclusive behind-the-scenes cover shoot for the September 2012 issue of Men's Health.

Also (and this seems like a strange thing to mention, but it's true), his most prominent trait is a pinkish brown skin tone that seems utterly foreign in L.A., for the sole reason that it's a natural tan, not sprayed on or salon acquired. A surfer's tan.

"I surfed competitively from age 13 to 18," Hemsworth tells me in a California-mellowed Aussie accent. "Every day, before and after school. I wanted to surf for the rest of my life. It's what all my friends did—I even had it as a subject in school for a number of years."

Wait. They teach surfing in Australia? You mean, as a class?

"Yeah! They teach you all parts of the surfing industry. How to judge surf heats, that sort of thing. Now I try to go to Indonesia whenever I have enough time."

Surfing seems like one of those sports, I suggest, that includes frequent confrontations with death. Drowning, for instance. Or sharks.

"Well, yeah," he laughs. "The fear of dying? That's part of the fun of it. The adrenaline you get from surfing big waves. I've seen a shark before. You get the worst wipeouts when you're not expecting it."

With this revelation, I mentally award him 10 interest points.

"When I was a kid, one time I got my leg rope wrapped around my whole body like a ball, under water. Couldn't get up. I was in waist-deep water, but I almost drowned. You know, I've had a few times." He laughs manfully, in an "I've faced death and lived to tell it" kind of way.

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A waiter arrives; Hemsworth pauses from the topic of his own mortality to accept the fries, which he then douses with a worrisome amount of Tabasco. (Ten more interest points. After all, capsaicin—the chemical in peppers that gives them their bite—boosts your metabolism and burns fat faster than almost anything else in your diet. Find out 15 More Fired-Up Foods that Burn Fat.)

The physical challenges presented by Hemsworth's workouts for The Hunger Games were strenuous.

"My character was spending most of his life in a state of hunger, and I wanted to get a sense of that, physically and mentally," he says.

With the help of his trainer (a former Navy SEAL) and a sparse variation of the Paleo diet, the actor dropped 20 pounds in the month before filming.

As with any weight-loss regimen, exercise and diet played equal roles: Hemsworth's 5-or 6-day-a-week workouts with his trainer included "throwing around tires, ropes—all sorts of unorthodox stuff that you wouldn't normally do in a gym." The main goal, he says, was to sweat for 90 minutes.

"The Navy SEAL was awesome. I always love hanging out with security guards or Marines—real men—because they're the most focused, professional people. And my trainer was a great guy ... who made me want to die for an hour.

"Training for The Hunger Games, I literally had to wait a half hour after each session before I drove anywhere," he says. "I had to lay on the ground until I could breathe properly again."

Which brings us to the second part of the regimen.

"It was tough," Hemsworth admits, "because I'm an eater. If I have one addiction in life, it's probably food."

But he managed to limit his intake to lean protein, vegetables, and fruit. As a result, he found himself frequently "in a really bad mood, with a short attention span and a short fuse."

Hunger will do that to you.

For his role in The Expendables 2, Hemsworth reversed the routine. As sniper Billy "the Kid" Timmons, he wisely put on weight so he could hold his own against costars Sylvester Stallone, Jason Statham, Bruce Willis, Arnold Schwarzenegger, and Jean-Claude Van Damme—real heavyweights in more ways than one. His most cherished memory from the shoot came when Van Damme unexpectedly kicked him in the chest.

Hold on, I say. Did you know the kick was coming? Was it scripted?

"No," the actor cheerfully replies. "He wasn't supposed to kick me."

And yet Hemsworth did not resent the surprise attack. "It was a present from him, in a weird way. I was honored to be kicked by him."

When not suffering blows from belligerent Belgians, Hemsworth maintains his fighting form through boxing, running, and surfing. Boxing is his current sport of choice.

"I love going to the gym, sweating, running around, feeling like I'm having a heart attack. I like the physical side of boxing—it's fun to punch a bag for 20 minutes—but I also feel mentally strong when I box," Hemsworth says. "I feel good in my own body."

As kids, Liam and his brother Chris were workout buddies. "We used to wrap towels around our hands and use them as clubs for sparring matches in the family room," Chris told me over the phone from London, where he was shooting the film Rush. When I asked who ruled victorious in those early matches, the actor's response (prefaced, please note, by a hoot) was a tidy thesis of friendly sibling rivalry: "Me, obviously," Chris said. "But I'm sure Liam would say differently."

Hemsworth is that rare celebrity who seems genuinely unobsessed with his body—a guy who relies more on common sense than trends or hyperspecific diets to stay in shape. He goes to the gym three or four times a week, not every day. He eats normal food. Sometimes he indulges; sometimes he cuts back.

It's a refreshingly uncomplicated, unencumbered, inexpensive regimen. It's a routine that your father or your grandfather might have followed. (Not every man can score a six-pack with such ease. If you're ready to work hard to earn the best body of your life, check out Speed Shred, the intense new fat-blasting 8-DVD metabolic training series from Men's Health.)

His daily diet is a relaxed rotation of oatmeal, fish, asparagus, and homemade chicken stir-fry loaded with chopped vegetables. Add in scrambled eggs with vegetables and a sweet potato or dose of brown rice if he's craving carbs.

Which isn't to say he's averse to the occasional Krispy Kreme binge—original glazed, please, and in mass quantities. "You gotta get, like, 24 and eat all of them," he recommends. "I lose my mind. Go crazy. Krispy Kreme fever!"

Click here to read more on Liam from Men's Health.