Credit: Charles Eshelman/FilmMagic

How did Ashley Greene get fit for New Moon?

"It was really easy," the actress, 22, told Saturday at the Magnificent Mile Festival of Lights event in Naperville, Il. "We were working 12 hours a day, so it didn't leave too much time to eat."

After her response, her publicist nudged her, but Greene didn't seem to care about her blunt answer.

When she did eat, she chose "really healthy stuff, which was nice."

Greene also said that training extensively for the sequel -- which had the third biggest box office opening of all time -- accounted for her figure in the movie.

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"We had a personal trainer and then we also had fight training," she told Us. "It was a good four hours a day of training."

To stay in shape these days, she said she does Pilates, usually six days a week.

"I do it early in the morning. It wakes you up, and it's kind of refreshing," said Greene, who is headed to London in a few months to begin filming the thriller The Apparition. "And that is basically it. Sometimes cardio. I am not a big weight person because when I do weights I build muscle mass."