Jennifer Aniston says Justin Theroux will ''put a gun to her head'' if she has surgery on her face.

The 45-year-old star insists she would never go under the knife in an attempt to try to stay looking youthful because her fiancée would not approve, but she also wishes she could ''beg'' her friends to stop injecting ''s**t into their face''.

She said: ''I think what doesn't work is seeing women trying to stay ageless. I'm grateful to learn from their mistakes because I am not injecting s**t into my face.

''But each to their own. I don't judge but sometimes I wish I could beg the people I am very near and dear to not to touch their face.

''I have a fiancé who will put a gun to my head if I touch my face in any way.''

The 'Horrible Bosses 2' actress admits she gets a lot of sleep and does plenty of exercise in an attempt to stay looking invigorated, but also joked the odd dry Martini has played a part in her youthful looks.

When asked what keeps her energised, she added to OK! magazine: ''Proper sleep, exercise, vitamin B12 shots. Also, it's not looking at the future and seeing what lies ahead, like, 'Oh my god, how am I going to do this?

'''Are we going to get on the plane, do we sleep, do we not sleep? We land so late in the afternoon and then when we do go back to sleep and think about the morning?' And a dry Martini helps!''