Jennifer Aniston let herself 'fall apart physically' in new movie 'Cake'

Actor Jennifer Aniston listens during a press conference for 'Cake' at the 2014 Toronto International Film Festival in Toronto on Tuesday, Sept. 9, 2014. (AP / The Canadian Press, Hannah Yoon)

TORONTO -- The typically poised and polished Jennifer Aniston says she let herself "fall apart" to play a woman in chronic pain in her new film "Cake."

The actress -- perhaps most famously known for her role on hit TV show "Friends" -- said she immersed herself in her character.

"I let myself pretty much fall apart physically and that was really important for me, emotionally and physically," Aniston said during the Toronto International Film Festival.

"I pretty much lived and breathed these people for the five weeks that we were doing it."

Aniston said she spent a fair amount of time preparing for the role of Claire, a physically and mentally scarred woman in a chronic-pain support group who begins to probe the suicide of a group member, played by Anna Kendrick.

"I did quite a lot of homework," Aniston said.

"I have two girlfriends who have suffered from chronic pain and one who is actually a dear friend and a stunt woman who experienced a very severe accident and became addicted to pain meds."

The actress said she asked those women about how they coped with their pain, and also spoke to doctors about the medication that would be taken by the character she played.

"For me it was really important to be true to what the medicine that I was taking physically would be doing to my body and at what point," she explained.

"That was actually kind of my biggest challenge as we were shooting out of order -- having a ledger of where I was in my pain management and my physicality."

The lengths to which Aniston went did eventually take a toll on her body, she said.

"I wore a brace which someone told me was a brilliant idea, because I tend to slouch and it helped me to just keep that (posture)," she explained. "It turns out if you walk like that for five weeks you do start to actually become in pain.

"The one thing I did have to do was have some treatments on the weekends because I would have pinched nerves and pinched this and pinched that, just from the physicality of it."

Despite the gruelling nature of her work, Aniston said she "loved every minute" of playing an unglamorous character.

"It was extremely liberating to do that. I loved it. Because you know as women, we do feel we have to live up to an expectation," she said.

"The truth of the matter is that that's just not the way it is. We don't always have our high heels on; we don't always have our makeup on. This character was someone who had just basically given up on just even waking up sometimes. That's what it required. That's how I approached it."

The film is directed by Daniel Barnz and also features Sam Worthington -- known for his lead role in "Avatar" -- and Adriana Barraza.

The Toronto International Film Festival runs until Sunday.