EXCLUSIVE: Lily Collins on Playing an Anorexic Following Her Own Eating Disorders: 'It's a Topic That's Taboo'

The actress explained why her role in 'To the Bone' is the most personal of her career.

Lily Collins is opening up about playing a woman battling anorexia in To the Bone following her real-life struggles with an eating disorder.

“It was an entire physical experience, emotional experience,” the actress told ET’s Lauren Zima at the EE British Academy Film Awards nominations event earlier this month. “But I was supported, and it's a really important story to tell.”

WATCH: Lily Collins Shuts Down the Golden Globes Red Carpet in Stunning Gown

“It’s a topic that is taboo, I think, with young girls, and it's really important to tell a story with this subject matter in the way that we tell it,” continued Collins, who is also the daughter of singer Phil Collins. “And, I'm so proud of it, and I'm excited that we're going to Sundance.”

The 27-year-old actress revealed her struggles while talking to IMDB Studio during promotional duties for the Marti Noxon-directed the Sundance Film Festival in Park City, Utah, over the weekend.

“This was definitely a more dramatic role for me. I suffered with eating disorders when I was a teenager as well,” she said. “I wrote a book last year, and I wrote my chapter on my experiences a week before I got [writer-director Marti Noxon's] script. 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.”

The Mortal Instruments star added that she shed pounds for the role with the help of a nutritionist, admitting that the weight loss took her mind back to her own battle with the illness.

“It did require a different set of emotional skills, to go back in time for me, with my experiences,” she shared. “So definitely a different type of film for me to do, very, very personal.”

WATCH: Lily Collins Strips to Find Perfect Gown for the Golden Globes

also took to social media over the weekend to share how “fulfilling” it felt to finally open up about her struggles.

“What a huge moment this is for me,” she captioned a cute jumping shot from Sundance on Instagram. “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.”

See the actress chat to ET at the recent Golden Globe Awards in the video below.