Mischa Barton has been taking mushroom-based diet pills

She told MailOnline: "As someone who naturally struggles with their weight, I wanted to find a supplement which worked in harmony with my body.

"I use Proactol XS as it has no side effects, is sourced naturally and lets me manage my weight safely."

And the former 'O.C.' actress is delighted with her results so far.

She added: "So far I've lost around 4lbs a week by taking the supplement."

The pills claim to work by forming a gel-like substance in the stomach which removes fat and cholesterol when it mixes with food, and then passes through the body naturally.

Mischa recently suggested she regretted accepting the role of Marissa Cooper on 'The O.C.'.

Asked if she would do the show again, she said: "Probably not... It's something I came so close to not doing. I had a really great thing with film. People say be grateful for what you have but it [is] certainly not the kind of thing I was expecting it to be... I've kind of seen it all."