Lily Collins says 'To the Bone' represented a ''form of recovery'' from her eating disorder.

The 28-year-old actress developed anorexia and bulimia during her teenage years, and has admitted she's benefited from the experience of playing a 20-year-old anorexic girl called Ellen in the new Marti Noxon-directed movie.

She shared: ''It was a new form of recovery for me. I got to experience it as my character, Ellen, but also as Lily.

''I was terrified that doing the movie would take me backwards, but I had to remind myself that they hired me to tell a story, not to be a certain weight.

''In the end, it was a gift to be able to step back into shoes I had once worn, but from a more mature place.''

Lily also revealed her darkest day on set came when she had to strip off and have her photograph taken by her on-screen stepmother, played by Carrie Preston.

Recalling the specific scene, Lily told the Daily Mail newspaper: ''I didn't realise she would really photograph me on her iPhone, but she did. Then she showed it to me and said: 'This is what you look like. Do you think this is beautiful?'

''I was shocked by how I looked. It was a moment that resonated a lot, not just as my character but as me, because I was actually seeing myself.''

And Lily insisted she's now finally let go of the desire to feel ''perfect''.

She explained: ''From a young age I've had a desire to put forward this perfect image, whatever perfect was. So even though there was all this un-prettiness going on inside me, I wanted to make sure that my appearance and composure were a certain way .

''Now I feel like I'm starting with a clean slate, so when I take a role I can let go more.''