To transform into her role as "pale, anorexic" Lisbeth Salander in The Girl With the Dragon Tattoo, Rooney worked out nonstop and based on this excerpt from an interview in Vogue magazine, she may have been on a bit of a diet:
When a waiter appears to take our order, we are all looking at our menus, but I see out of the corner of my eye Fincher nudging Mara. He says with quiet seriousness, "You can eat." I look up to see her reaction. Mara rolls her eyes, and Fincher laughs. "You can have lettuce and a grape. A raisin if you must." She orders a piece of fish and barely touches it . . . I ask if she had to get unhealthily skinny for the role. She says, "Umm . . . not really." It hasn’t been too hard for her," Fincher quickly adds.