The Pitch Perfect star used food as a way of "numbing emotions" and as a defence mechanism to hide her insecurity at not being a "natural performer".
She explained: "I knew deep down inside that some of the emotional eating behaviours I was doing was not healthy. Like I did not need a tub of icecream every night.
"That was not, that was me kind of numbing emotions using food, which wasn't the healthiest thing.
"I think it was dealing with not being a natural performer, and having to perform every day. And that pressure and internal stress to be able to perform like that."
The Bridesmaids actress previously revealed that losing weight has helped her to get in touch with her "inner siren".
She said: "I grew up not really trading on my looks - I was the personality girl. But after going through my whole health transformation last year, I've been in touch with this 'inner siren'."