A “balanced” diet of fast food and fattening corn chips helped Matt Damon get good and “doughy” for his big screen portrayal of federal whistle-blower Mark Whitacre in the upcoming film The Informant.

The big screen’s “Jason Bourne” had to pack on 30 pounds for the role.

“I started eating like crazy and drinking dark beer. Between meals on set, I’d eat a No. 1 Value Meal at McDonald’s and then Doritos on top of it. It was absolute heaven,” Matt tells Entertainment Weekly.