A friend of Fox's told Now magazine: "She's already lost almost a stone in the last eight months. But she wants to lose more because she thinks it'll help her be taken more seriously as an actress."
"She wants proper dramatic roles and she believes losing her curves will help her do that. She'd like to do period dramas like Keira Knightley, not just been seen as a sex symbol."
They continued: "If she can't count all of her ribs she feels overweight. She's trying on size 0 pants from summer and they hang off her. When she was working on Transformers she was a healthy 8st, but now she's a tiny 7st 4lb."