Mark Wahlberg dropped by the Jimmy Kimmel Live Tuesday night to promote his new film Pain & Gain, which is set for an April 26th release date, and discussed his diet for the film.

The film is about two steroid-abusing bodybuilders from Florida who accidently get mixed up in a kidnapping and extortion plot. Just by browsing some of the photos, movie posters or TV spots, it's more than evident that Wahlberg has put on some considerable size to match that of his co-star Dwayne "The Rock" Johnson.

Wahlberg has always been known for being one of the more fit celebrities in Hollywood, evident in his role in The Fighter. He spoke about the change in his weight on Tuesday.

"It's funny because when I was training for the movie, I was 165 pounds. I did four movies last year. For the first movie, I had to get as thin as possible. For this one, I had to get as big as possible -- then I had to lose the weight in 30 days," Wahlberg told Kimmel. "I went from 165 to 212, and then I went back down to 180 in 30 days, and then I went to SEAL training and did a movie afterwards, the Marcus Luttrell film."

So how did Wahlberg put on so much weight and bulk in such a short amount of time? The 41-year-old actor said he ate 10-12 meals a day and loaded up on supplements.

"I started eating whatever I wanted, so I was eating pancakes and stuff and that was fun, " he admitted. "But I was also developing my own supplement line, so I had access to the scientists that GNC provided me. I was getting all the best ban-free substances -- whey protein, mass gainer, my blast and burn packs."

When he was not eating, working out, or shooting the film, he was sleeping quite a lot. He said, "They call them growth naps."

"You workout in the morning really hard and then you eat throughout the day. Then, you just nap," he added. "You're either resting or eating."

Tags: Mark Wahlberg