Jessica Biel has admitted that one of her biggest fears is losing her good looks to old age.

The US star – who is known for her stunning looks and athletic frame – says that she has already noticed her body getting older.

Jessica told Marie Claire, "I don't know how I'll cope with ageing - I better start figuring it out. I feel my knees changing - like, why do I have this pain when I'm running on the treadmill?

"And I'm definitely fearful in a very vain manner about my body ageing.

"I think it's freaky weird to look at a picture of your grandmother when she was a young woman and look at her now."

Yet the actress turns her nose up at having any plastic surgery.

"I am really afraid of blades on my face - that freaks me out beyond belief. I would way rather have wrinkles than have some slice-up going on."

At least Jessica has boyfriend superstar Justin Timberlake to keep her feeling young and beautiful.

See Jess and Justin holidaying in Rome here