Scottish actor James McAvoy was struck down with bowel problems after adopting a fattening diet for new movie Filth.

The Atonement star appears in the film adaptation of Irvine Welsh's novel, and he piled on the pounds to play a dysfunctional detective.

MCAvoy binged on junk food to help him gain weight, but admits the fatty diet made him sick.

He says, "I went to the doctor at one point because I was having a lot of problems with my bowels. He said 'You either have ulcerative colitis (a form of inflammatory bowel disease, Ibd) or your body is trying to reject what you are doing to it.'

"I was trying to drink loads of Guinness and Coca-Cola and eating loads of burgers and chips and fish suppers because I was trying to put on weight. My body started to reject it about a week into filming."