Lily Collins was nervous about losing weight for her new movie because of her previous battle with an eating disorder.

The actress stars as Ellen in To the Bone, about a young woman dealing with anorexia. The part was a particularly poignant one for 28-year-old Lily as she’s also suffered with eating disorders, which she opened up about it in her book Unfiltered: No Shame, No Regrets, Just Me, which was released earlier this year (17).

"I was nervous right away with the subject matter, but I knew it was for a greater purpose. I'm older now and I have a different perspective on it,” she said on British show Lorraine.

"I was excited to be able to tell this story and open up the conversation for men and women around the world."

She added that she was kept under close supervision by “the producers, the directors, the writer, my mother and also a nutritionist”.

"We worked very closely together, very healthfully,” she smiled.

Lily is the daughter of music icon Phil Collins and his second wife Jill Tavelman.

To the Bone, which also stars Keanu Reeves as an unconventional doctor who challenges Ellen to face her condition and embrace life, premiered at the Sundance Film Festival in January and hits cinemas from July.

“It’s actually the first feature film that’s ever been done about eating disorders,” Lily shared. “I feel so proud to be a part of it. I’ve been very vocal about my experiences in the past with my own eating disorders.

“I think it’s a subject matter that’s considered quite taboo to talk about nowadays even though the fact it’s becoming more and more prevalent in youth with men and women. To do it in a film, to make it entertaining in a way, but also keep it very informational is important.”