Lily Collins' new role forced her to relive her teenage battle with an eating disorder.

Lily Collins has opened up about being forced to relive her teenage battle with eating disorders while shooting her new film ‘To the Bone’.

Playing a young woman dealing with anorexia meant Collins was confronted with a long-held fear, the actress admitted in an interview with IMBD.

“I suffered with eating disorders when I was a teenager as well,” she told the interviewer in the IMBD studio at Sundance Film Festival in Utah, USA.

“I wrote a book last year, and I wrote my chapter on my experiences a week before I got [director Marti Noxon’s] script, and it was like the universe putting these things in my sphere to help me face, kind of dead on, a fear that I used to have.”

‘To the Bone’ centres around Collins’ character Ellen trying to recover from anorexia with the help of an unconventional doctor played by Keanu Reeves.

In preparation for the role, the 27-year-old actress had to lose weight, which she said happened under the careful guidance of a nutritionist.

Perhaps even more dangerously, the actress was also forced to relive a difficult part of her life while playing the role of Ellen.

"It caused me to have to emotionally go there, but in a way that was the most safe, healthy way possible with a nutritionist, and really to physically go there but also emotionally," she said.

"And it did require a different set of emotional skills, to kind of go back in time for me, with you know, my experiences."

She described the film as "very, very personal", but hoped that the first-hand experience of eating disorders that she brought to the role would help push the films' subject into the limelight.

Collins said she felt the universe had given her a way to explain eating disorders "as someone who’s gone through it".

"And to open up a topic that is considered quite taboo with young people nowadays — male, female — and to really start a conversation," she added.

Listen: Meshel Laurie talks to a woman battling anorexia. 

The actress continued the conversation on Instagram, with a post of herself in the snow uploaded shortly after the interview.

In the post, Collins told followers she was "chilled to the bone but feeling so free" after the "huge moment" of revealing her past struggles with eating disorders.

Chilled to the bone but feeling so free. What a huge moment this is for me. Owning my past, being open, and having no shame or regrets about my experiences. Sharing my history with eating disorders and how personal this film has been is one of the most fulfilling experiences of my life. Thank you for all your love and support. I'm sending all of mine right back (especially today!) and remember, you are never ever alone #Unfiltered...

A photo posted by Lily Collins (@lilyjcollins) on Jan 21, 2017 at 3:11pm PST

"Owning my past, being open, and having no shame or regrets about my experiences," she wrote.

"Sharing my history with eating disorders and how personal this film has been is one of the most fulfilling experiences of my life."

Lily Collins memoir, Unfiltered, in which she discusses her eating disorders among other areas of her life will hit bookshelves in March.

'To the Bone' premiered at Sundance Film Festival on 22 January.

Eek! That's me! Doing another read-over of my new book — can't wait for it to come out THIS year so you can all read it too! #LivingLifeUnfiltered...

A photo posted by Lily Collins (@lilyjcollins) on Jan 2, 2017 at 4:34am PST

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