Gyllenhaal gained 15lbs of muscle to play a middleweight boxer in the movie ‘Southpaw,’ by working out six hours a day for six months, including at the Las Vegas gym of Floyd Mayweather, the champion boxer.

Southpaw’s director, Antoine Fuqua said that “We literally turned him into a beast. Jake, my god, he’s a very electric, powerful fighter in this movie. He’s so committed and gives his heart. The word is sacrifice.”

He was spending so much time in the gym and was so committed to the role that his relationship with Alyssa Miller ended. “The amount of time you have to put into it, the sacrifice that you put into your body, it's not something that you're eager to do again. It's a huge commitment.” Gyllenhaal said about his gruelling preparation for the role.