"I had terrible bulimia for about a year. I've still got the scars on my knuckles from where I put my fingers down my throat," the People quoted Newton, as saying.
The 34-year-old's bulimia turned worse once she reached her early 20s after a series of unworthy relationships.
"I'd been involved with this guy for a long time, he was much older than me and I felt a lot of shame about my sexual relationship with him. would have these dinners with him and then go back to the flat and I'd throw up," she said.
"Then I went out with someone who was emotionally abusive, criticizing me the whole time," she added.
The 'Pursuit of Happyness' actress, who is now married to screenwriter Ol Parker and has two daughters, sought medical help when she went Los Angeles to shoot a film.
"I saw a therapist for the first time. After that first session, I never threw up again. I had made the connection between shame and self abuse," she said.