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Matt Damon has lost or gained substantial amounts of weight for his past film roles, but he recently told Us Weekly that his strict diet for "Elysium" was the hardest.

"I was grumpy on this set, because I was on a diet for the whole movie," he said, explaining that he tends to "shut up" and keep to himself when he can't eat how he likes.

"It was really hard because I love to eat and I love to drink," he added. "I'm at the point in my life where somebody was silly enough to marry me and won't leave me if I put on a few pounds."