Mischa Barton reveals the secret behind her tiny waist

The OC star Mischa Barton has revealed that pilates is the secret behind her slim frame.

"For me, it's all about pilates recently," Barton said. "I'm obsessed with pilates. I think it's so fun."

The 23-year-old British actress had recently sparked concern for her health after displaying an increasingly thin physique, reports the China Daily.

Barton hit out at critics of her weight loss, insisting she has never embarked on faddy diets or extreme exercise regimes.

She told America's OK! magazine: "I don't do any crash diets. There's nothing that I really do like that, because I'm always working. I mean, before I go do a film, I do work out more. I do get ready for a film and try to be healthy and in shape. And when I'm not working, I do less of it.

"I do more cardio because I work long hours. Jogging, running — stuff like that's really good before you do a film so you have more energy."