has revealed that she became quite grumpy when she stopped exercising in order to get into character for Golden Globe-nominated film Cake.
"It's interesting when you stop exercising. It really was interesting how my serotonin levels went down. My stamina was shot. I was cranky. I was irritable," Aniston, 45, said.
"I'm usually really not any of those things. I found myself short. I was hungry like crazy," she added.
As previously reported, the star often went without makeup and stopped working out for two months to play Claire Simmons, a woman who suffers chronic pain after a car accident, said Us magazine.
But for Aniston, not looking like her red carpet self wasn't the downfall of not hitting the gym.
"You realise exercise is just so important to our soul. Not just being able to fit into skinny jeans, to your state of mind, your soul, all of that.
"I surrendered into it. I actually didn't fight it. I didn't think oh this is horrible. It was such a part of what I enjoyed about mining this character."