Matt Damon realized it was time to shape up and trim down his waistline when his stepdaughter nicknamed him “Matty Fatty”.

The Hollywood star piled on the pounds for recent roles in The Informant! and to portray South African rugby captain Francois Pienaar in the new Clint Eastwood movie, Invictus.

Damon confesses he didn’t realise just how big he had gotten after filming on Invictus wrapped and was convinced his clothes had shrunk in the wash.

Even a quiet word of advice from his wife Luciana wasn’t enough to send him running to the gym.

He says, “My wife thinks I have a condition: the opposite of anorexia. I look in the mirror and I think I look great. We had to go to some film function and I put on a suit. I put it on and it came up to (my forearm). I thought, ‘That’s strange, my suit’s shrunk.’ So I put on another one, and same thing. Third one, same again. So I said to my wife, ‘Honey, this dry cleaner is no good. These suits were tailored for me.’ And she’s going,’ OK, do you think maybe you put on about 30 pounds?’”

It was only when his stepdaughter Alexia poked fun at his weight that he decided to get fit – but not before suspecting his prankster pal George Clooney was behind his ill-fitting clothes.

He explains, “The situation resolved itself when I said to my stepdaughter, ‘Come on, it’s time for dinner.’ And she goes, ‘OK Matty Fatty!’ Before, I thought it was more likely that George Clooney had hired someone to tailor my suits!”

Source, Bauer-Griffin