Jake Gyllenhaal lost some 25 pounds to look rail thin in the new film "Nightcrawler," but the versatile actor will be back in fighting shape in the upcoming boxing drama "South Paw."

In a transformation similar to Robert De Niro's physical fluctuation in Martin Scorsese's 1980 "Raging Bull," Gyllenhaal packed on 15 pounds of solid muscle in order to play Junior Middleweight Champion Billy "The Great" Hope in theAntoine Fuqua-directed film.

Check out the massively-muscled Gyllenhaal below:


The photo debuted on Deadline.com.

"Southpaw" is being directed by Fuqua ("Training Day") from a script by "Sons of Anarchy" creator Kurt Sutter. The Weinstein Company will release the film sometime next year.

The studio unveiled a demo reel from the film -- set to an Eminem song -- at the Cannes Film Festival in May. 

Dave Lewis has been a Los Angeles-based entertainment writer and editor for nearly ten years. Originally hailing from Minneapolis, he moved to L.A. in 1996 to attend USC, before working for various periodicals and web sites including a lengthy stint at Variety.com. He joined the HitFix staff in 2011.