The 37-year-old "Knight and Day" star, who was photographed by Terry Richardson, tells the magazine she works out "five days a week" because she doesn't want to get too skinny.
"Exercise for me is like eating, sleeping, and breathing," says Diaz, insisting that the to-die-for body everyone talks about "is not me trying to stay slim, it's the one where I work hard to keep weight on me."
And, she adds, "The more I work on my body at this age, the better it gets."
That includes her booty. "I have a little one, but," she notes, "it is, nonetheless juicy."
Diaz shows off her assets in the accompanying feature, which has her posing atop a New York City skyscraper in a variety of '70s-inspired ensembles.
The blonde stunner models looks including a chic gray Marc Jacobs suit with Portolano Products gloves and Alexander Wang booties; a sexy Salvatore Ferragamo number consisting of hot pants and a jacket over a shiny bodysuit, with chunky black boots and a cocked hat; a camel MaxMara coat with stiletto boots; a camel Chloé jumpsuit with Christian Louboutin booties; and an elegant gold slit-leg Balmain gown with Giuseppe Zanotti for Balmain boots.
Despite wearing clothing well, Diaz, a fan of J Brand and Acne jeans, says getting red-carpet ready isn't always easy. "It's hard out there, man. We're all choosing dresses from the same places," she explains. "I really like Victoria Beckham, though." Still, she admits, "I'm so confused at this moment. I don't understand fashion at all right now."
"I'm appreciating my skin and my wrinkles and all those things because you cannot stop aging, you can't... The only way to stop it is if you die. But that's not a great alternative."
Diaz says she looks to mature leading ladies like Helen Mirren for inspiration. "That woman is drop-dead sexy. She's not trying to turn back the hands of time, she is just taking care of herself." And, best of all, Diaz adds, "She's a nudist!"
We guess this means we'll be seeing Diaz in a bikini when she's in her 60s -- or maybe in nothing at all!
In related news, check out Helen Mirren posing topless in New York magazine.