Zac Efron, 24, starred in 'The Lorax,' last month. The heart-throb is now doing promotions for his next film, 'The Lucky Ones,' a film based on a book by Nicholas Sparks. The former 'High School Muscial' star plays a marine in this upcoming role.

Efron has to endure a workout regime before being production to get in shape. He talks about his plan during the interview with Men's Health.

"Physically I started eating a lot. Eating through walls. Just eating and eating," he said.

"That's all I'd do and I put on some weight that way. As far as the training goes, just trying different techniques and methods. It's one of the only concrete things that you can do to feel differently about a character. I didn't feel like a Marine. I didn't have the posture. I didn't feel like I had the presence and that was just one thing for me that I could do to really up that change," Efron continued.

Efron was really impressed by the "presence,' as he stated, that Marines and the Navy SEAL possess.

"When I went in to meet some of these guys, the sergeants, I was blown away. I was taller than most of the guys, but they were just thick, like there was something about them. They had a definite presence. Here I am, slouched over and I just smile a lot. I'm just always smiling. These guys were always serious. Honestly, it was one of the most awkward moments in my entire life," he stated.

Check out the full interview in Men's Health!