Denzel Washington gave up booze to play an alcoholic in Flight over fears the role could prompt a drinking binge.
The actor has picked up an Academy Award nomination for his portrayal of troubled airline pilot Whip Whitaker, but he reveals he remained teetotal throughout the shoot so he would be at his best.
"I absolutely did not drink the entire picture," he told Britain's Seven magazine.
"Normally I might have a glass of wine after work or something like that. But on this one I was afraid I might get too into it, and I just wanted to be clear. I want to give 100 per cent of myself and I want to be focused. Nothing would have been worse than drinking on the set. And then you might think you were good and you'd be awful."
Instead, Washington prepared for the role by watching clips of drunks on YouTube and indulging in his favourite foods so he would look bloated.
"I ate a lot," he recalled. "I ate what I wanted and I ate late at night. I would come home from work, I didn't overeat. But if I wanted a hamburger and fries and shake and a piece of apple pie with icecream on it, I had it.
"I knew this was a man who drank and did drugs. He's not going to be going to the gym and he's going to be not sleeping enough. [I] wanted my gut to be hanging out. You've got to go there because that's who he is. There's no cute version."
Where: Opens at cinemas on February 7