Channing Tatum lost 15lbs in one day.

The 'Foxcatcher' actor underwent a gruelling regime to portray wrestler Mark Schultz in the movie and admits he and co-star Mark Ruffalo resorted to extreme lengths to get into the shape they needed to be in.

He said: ''I dropped 15lbs in a day. You have a ton of water in your skin and stomach and Ruff and I figured out how much weight we could lose in the gym.

''I was not feeling very well after that.''

The 34-year-old hunk admires his character from the film because wrestling takes much more discipline than acting.

He explained: ''To win Olympic gold, you train from childhood. There's no just jumping in, saying, 'I'm really gifted.' It's a day-in, day-out obsession.''

Channing never formally studied acting so views his work on movie sets as his training.

The former stripper told heat magazine: ''I had on the job training. Each film has been a school term. It's an expensive education.''

Though the 'Magic Mike' actor is enjoying a strong career, he still regrets roles he lost out on.

He said ''I've not cried about losing a part but I really, really wanted 'John Carter'. It's one of those that got away.''