James McAvoy says the muscle-gain supplements he used to bulk up for Wanted had a nasty side effect

James McAvoy reveals violently farting

'To be fair, it really helped but it came with a massive side effect of me violently farting,' he says.

'It was so often and so vigorous, I couldn't stop. When I was filming I was by far the biggest farter in Hollywood.

'I had to give up the shakes after a month and start eating chicken and steak instead as it was getting embarrassing.'

'I found that caffeine, alcohol and smoking break down muscle,' he tells The Sun, 'and there was no way I was giving them up.'

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