Lily Collins
Credit: Rick Kern for Stella Artois/Getty

In To the Bone, Lily Collins plays a young woman battling anorexia—and it turns out the subject matter is personal. While promoting the movie over the weekend at the Sundance Film Festival, the actress revealed that she had an eating disorder in high school (something she plans to expound upon in her upcoming memoir). “I randomly wrote a chapter about it the week before I got the the script,” she said after the world premiere yesterday afternoon. “It was the universe saying, ‘There’s a reason that you’re talking about this right now. There’s a bigger story to be told.’”

The story in question centers on Ellen, a 20-year-old college dropout with a penchant for drawing who repeatedly enters treatment for anorexia. It’s based loosely on unREAL co-creator and first-time director Marti Noxon’s own experiences with the disease. Unsurprisingly, the narrative is dark, but there’s a spatter of funny moments, like when Ellen and another patient go out to a Chinese restaurant and beg the waitress to serve them beer. Even though Ellen doesn’t swallow her food, the laughter at the table gives the audience hope that one day she will.

“There’s a humor that you understand if you’re in the mindset of the disease, but it’s also a very dramatic disease,” Collins added. Preparation for the role had its own set of challenges, too. Due to the short production schedule, Collins had just two and a half weeks to lose enough weight to convincingly look the part, which she credits to the help of a nutritionist, along with the hair, makeup, and wardrobe departments. “Given my past, it was important to me that the physical state mirrored the emotional state,” she said. Here, Collins talks more about the film and her former disorder.

What prompted you to speak out about your past?

It would’ve been unfair of me not to because it is a huge reason why I chose to do the film. I saw it as an opportunity for me to start a conversation with young people about a topic that is considered so taboo nowadays but is becoming more and more prevalent. The second you speak up and admit something, you realize you’re not alone. The amount of people that come forward is staggering.

Was filming the movie a cathartic experience for you?

Completely. Had I not written that chapter in the book when I did, I probably wouldn’t have been as open and honest with myself about my relationship to the script. But I got to revisit my chapters while I was working, and then I would reread them to inform my character. It was very therapeutic.

Lily Collins Keanu Reeves To The Bone Still -Embed 2017
Credit: Courtesy Sundance Film Festival

How did you prepare for the role?

I did a lot of research about what it means to go through these diseases. I met with the head of The UCLA Eating Disorders Program, I went to an Anorexics Anonymous group, and I worked with a nutritionist to lose the weight. I really surrounded myself with facts, because it’s so easy when you’re younger to feel like you’ve figured it out yourself and not seek the professional help that you most likely need. It was interesting for me to step back into those shoes 10 years later with a greater understanding of why it happened to me then and why I chose to put myself through it.

What were the physical demands?

There was never a goal weight set, but I know how it feels to be deprived, and those raw, bizarre, lonely, controlling emotions in that physical state. That was important for me to convey. It was difficult to step back into those shoes, but the hardest part was afterward. When you have a disease, you’re used to losing weight—gaining weight is completely foreign and scary. However, that fear of being fat doesn’t apply to me anymore—I’m more about the fear of missing out and not living in the moment.

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Why did you decide to write a memoir now, in your twenties?

I’ve always loved writing. After I finished filming Rules Dont Apply in 2014, I went through a big growth period of thinking about things that I put to the side and hadn’t faced. I figured that it was time to talk about it. I’m an open book now.

This interview has been edited and condensed for clarity.