Jonah Hill's drastic diet caused problems for the director of new comedy The Sitter after the funnyman began to lose weight during the shoot.
Hill was filming the movie last year (10) when he decided to embark on a new healthy lifestyle and hired a nutritionist in a bid to slim down.
But filmmaker David Gordon Green admits it was a struggle to conceal the once-chubby star's transformation on the big screen.
He tells New York Post gossip column Page Six, "About two-thirds of the way through the movie, Jonah made a conscious decision to say, 'I want to get healthy, let's do this.'
"We shot the movie out of order, so that helped disguise it a bit, but there are some scenes where you can see his pants don't fit anymore. It forbid reshoots."