Matt Damon Says Gaining 30 Lbs. Was Easy – and Fun

By Peter Mikelbank

09/07/2009 at 02:45 PM EDT

Looking tanned and trim, Matt Damon declared his latest film challenge as "probably the funnest time I've had working."

He also enjoyed making the movie The Informant!

What PEOPLE's former Sexiest Man Alive was describing was adding 30 lbs. – not to mention the cheesy moustache, hairpiece and glasses – to become nearly unrecognizable for his role as Mark Whitacre, an agricultural company's vice president-turned-FBI informant.

"It was very, very easy to gain the weight," Damon told reporters at the Venice Film Festival on Monday. "It was very, very fun, probably the funnest time I had working because I didn't have to go to the gym after work and I just ate everything I could see."

Based on a true story, the comedy – which costars Two and A Half Men's Melanie Lynskey and Scott Bakula – is Damon's latest collaboration with Oceans director Steven Soderbergh.

In Venice with wife Luciana, Damon heads off to Toronto tomorrow for the film's North American debut just as pal George Clooney is expected to arrive in the Italian city for the red carpet turn of his film, Men Who Stare At Goats.