Jennifer Aniston

Jennifer Aniston is embarking on a new healthy lifestyle and has cut out cigarettes and eliminated caffeine from her diet.

And pals are convinced she means business after watching the 38-year-old in action on pal Courtney Cox's TV drama Dirt recently.

Dirt actress Laura Allen, who spent time with Cox and Aniston on the set, tells American publication Us Weekly, "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."

In addition to resisting the temptation to indulge in smoking, Aniston also managed to refrain from caffeine.

Allen adds, "I had a Diet Coke on-set and she was really jonesing (craving) for it!"