The Chloe actress said that size pressures within the industry require her to adopt a strict diet and fitness regime.
She told AOL: "I'm in my mid-20s and I know how to look after my body on my own. I'm not going to deny that I don't think about it every day, it's always on my mind. I clearly like being fit, but it's not thin without a hell of a lot of work - I run and I exercise a lot and then I eat.
"If I have to diet, it's salad with protein, salmon and broccoli, no dessert. But what kind of life is that? So I work out a lot and I'm just pretty moderate about what I eat."
She added: "I have to stay in shape because I'm an actress. It's f**ked up and it's twisted, but I wouldn't get the roles otherwise. If I'd been bigger, I don't think they would have cast me for Mamma Mia!."
