Jennifer Aniston has revealed she suffers from insomnia.

The 'Cake' actress, who is engaged to 'The Leftovers' star Justin Theroux, admits she has a ''hard time'' falling asleep at night and is worried it will cause her to die young.

The 45-year-old beauty said: ''I have a hard time sleeping. Sleep is a tough one for me. My brain, the committee in my head, if I wake up at three in the morning I just start having conversations and they won't shut up and then I can't get back to sleep. I do have three animals and a human being in the bed, so there are all these distractions.''

The former 'Friends' star has even downloaded an app to track her sleep patterns.

She told 'The Dr. Oz Show': ''I got an app on my phone that allows you to sort of track your sleep rhythms, like how deep you go. I don't really quiet ever get into the deep, deep, deep sleep. And am I going to die young?!''

Jennifer stopped working out to play a woman suffering from chronic pain in her new movie and admits it altered her mood and stamina.

She said: ''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. I'm usually really not any of those things. I just found myself short. I was hungry like crazy. Then, you realise exercise is just so important to our soul. Not just being able to fit into skinny jeans, just your state of mind, your soul, all of that.''

But the actress insists she wasn't upset about gaining weight for the role.

She said: ''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.''