Jennifer Aniston has quit smoking and caffeine as part of an extreme detox.

The former 'Friends' star - who recently made a cameo appearance in Courteney Cox's new series 'Dirt' - is purging herself of toxins in a bid to cleanse her system.

'Dirt' actress Laura Allen said: "Jen was doing a total cleansing. She did a lot of yoga to stop smoking.

"Between takes, it would have been tempting to go outside and have a cigarette. Instead, Jen was clinging to Courteney. She said how hard it was."

Jennifer, 38 - who was a chain smoker despite her healthy diet and exercise regime - is also struggling to get through the day without caffeine.

Laura said: "I had a Diet Coke on-set, and she seemed desperate for it."

The 32-year-old actress also lifted the lid on the lesbian kiss Jennifer filmed with best friend Courteney, 42, in the season finale of 'Dirt'.

She says : "Courteney has some steamy sex scenes. This was actually really tame."