Cameron Diaz, 43, says goodbye to tube tops

Cameron Diaz looks like she hasn't aged a day since "There's Something About Mary" in 1998 -- but the 43-year-old actress says it's time to start acting her age.

The first thing to go? Her signature tube tops.

"I'm definitely not doing tube tops. No way," she told Harper's Bazaar when asked about the one thing she wouldn't dare wear at 43.

The star, who believes in "dressing your age," added that "everybody's age is different."

"It's all a matter of how you present yourself, how old your spirit is, and where you are in your life. Some 50-year-olds are still 35. It's about expression and what they can pull off," she said.

See Cameron through the years:

While many people would kill for Diaz's long, lean body, she admits it's getting harder to maintain as she gets older.

"It doesn't react the same way that it used to. I don't get the results that I used to as easily as I once did ... If I slack off, things don't come back so easily. I have to be committed."

The actress is sharing all of her tips in her new book, "The Longevity Book." A follow-up to her previous No. 1 bestseller, "The Body Book," the educational page-turner taps into scientific research to explore how the female body ages -- and how women can maintain their "optimal health" as they age.

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