As well as being known as a Hollywood star, and for his brief rap career, Mark Wahlberg has always boasted a muscular physique, but the 43 year-old actor lost an alarming amount of weight and looked like a shadow of his former self in 'The Gambler.'

The Gambler
Mark Wahlberg in 'The Gambler'

Wahlberg lost a staggering 60 pounds for his role as Jim Bennett, an English professor by day and a high-stakes gambler by night, in the upcoming thriller, and at the AFI Fest premiere of the film in Hollywood on Monday (Nov 10th), he revealed why he had to be "as thin as possible."

"I went from 197 to - the lightest I'd ever been in a movie was in Boogie Nights, I was 138 - so I wanted to beat that," Wahlberg said at a post-screening discussion. "I beat it by a pound, so 137. I was losing weight while we were shooting the movie too so continuity kind of went out of the window."

More: Can Mark Wahlberg Finally Reach Oscar Glory In The Gambler?

Although Wahlberg risked his health for the demanding role, the film studio still wasn't completely happy with his transformation. The two-time Oscar nominee's lips were turning blue due to lack of nutrition.

"No energy, no nutrition, and the studio, there was a complaint about that, that my lips were always looking blue," he said. "What the f-k do you want me to do? I haven't eaten anything! If you make them red, I'm going to look weird, like I've got lipstick on, so it is what it is."

More: Watch 'The Gambler' Trailer Here

While walking the red carpet, Wahlberg also told E!News that he achieved the dramatic weight loss by maintaining a liquid diet or six weeks. "I was miserable because I like food," he explained. "Then, I had to exercise for two-three hours on top of shooting a 12-hour day. It was not fun." 'The Gambler' hits theaters on December 19th.