Inside Chris Messina's "Fun" Method of Gaining 40 Pounds for Live by Night

The Mindy Project actor debuts a new look in Ben Affleck's latest project

Chris Messina had to work hard for his body in Live by Night.

No, he didn't lose a dramatic amount of weight for the role; instead, The Mindy Project star had to gain a lot of weight...40 lbs. to be exact. And to put on the extra fluff, Messina had to completely change his diet, but he didn't complain.

"It was fun. It was a lot of fun," he told Stephen Colbert on The Late Show Wednesday night. "[I] just stuffed my face. Beer—lots of beer—bagels, pasta. I would have a beer by the bedside table, and I woke up in the middle of the night to pee and I'd just chug the beer."

With such a free-spirited approach to food and drink, Messina joked his co-stars loved him even more. "It was fun," he said. "I was like a hero on set."

Messina explained he had to gain the weight because his character in the book from which the film is adapted is described as "round."

"I'm [Ben] Affleck's sidekick and kind of, believe it or not, his bodyguard," Messina shared, "so I thought the only way to maybe do that is to have some bulk."

Messina and Affleck also co-starred in Argo, which took home Oscar for Best Picture in 2013.

Now that it has been a fair amount of time since Messina and the cast finished filming, the 42-year-old actor has lost the "fun" weight he gained.