The actor, who stars as champion boxer Micky Ward in the movie, had to endure a long-term diet but wasted no time in tucking into some tasty treats once it was all over.
Speaking at the Cinema Society premier of the flick on Friday, he told People that he ate 'everything' once filming wrapped.
'I just became obsessed with chocolate-chip cookies and stuff that I never really had any interest in eating [before],' the 39-year-old said.
But his wife, Rhea Durham, eventually stepped in and warned him off the unhealthy snacks.
'She said, 'You might as well take care of yourself,'' he explained. 'But I needed a break from it. Certainly four and a half years was very draining. I needed that time off, and now I need to get back in there.'