But as his roles as a ballplayer in Moneyball, a Navy SEAL in Zero Dark Thirty and now star of the new Marvel film Guardians of the Galaxy prove, the 35-year-old has also learned (sometimes the hard way) what it takes to get in amazing shape.
Starting at 250 lbs., Pratt says he first approached weight loss just like he did when he wrestled in high school.
"I was like, 'I'm going to cut weight, put on plastics, run and I'm not going to eat,' " he tells PEOPLE. "That's what I did, but I didn't realize how that affects your body long-term, so that the minute you stop doing that you balloon your weight back up."
The training also took a toll on the actor's body. To play a Navy SEAL, "I was doing 500 push-ups a day, working out at the gym, running five miles a day, but with no food, and I tore my body apart," he says. "I felt terrible afterwards, had to get shoulder surgery, and I wore myself down doing that because I didn't have the proper coaching."
Now starring as an interstellar thief in Guardians, the sculpted Pratt may have discovered the body type that fits him best.
"I actually lost weight by eating more food, but eating the right food, eating healthy foods and so when I was done with the movie my body hadn't been in starvation mode," he says. "It wasn't like I was triggered to just gorge myself and get really fat again."
In a role that called for ripped abs and bulging biceps, along with a healthy dose of charm, Pratt is confident that at least two of those three attributes won't be going away anytime soon.
"It's something that I think I can maintain because now I don't spend four hours in the gym each day," he says. "I do maybe one hour in the gym maybe four days a week, and that's it."
For more of Pratt's interview, pick up this week's issue of PEOPLE, on newsstands now.