Sienna Miller was called "Fatty Edie" by Guy Pearce during the making of "Factory Girl." The pair star in the film as artist Andy Warhol and his muse, Edie Sedgwick.
Guy dieted so much for his role as the slender pop artist he ended up thinner than Sienna, prompting him to invent the nickname.
Sienna revealed to Britain's New magazine: "Edie was unhealthily skinny. But it's quite funny that Andy was skinnier in the film. Guy was taking the p**s out of me a lot! He'd say 'Little fatty Edie!' He was so skinny!"
The 25-year-old actress also revealed the director tried hiding her food in an attempt to get her to lose weight for the part.
She said: "The awful thing was Guy was really disciplined about losing the weight and I wasn't. I didn't want to. The director used to steal my bagels but he gave up because I love my food.
"I'm an energetic person but I don't work out and I do eat a lot. So Andy was actually skinnier than Edie in the film, which is not how it was."