She may be a 43-year-old single mother of two, but bikini-clad Real Housewives of New York City star Kelly Bensimon looks like a sexy twenty-something on the cover of Shape's September issue.

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"My body is like a Ferrari," the Bravo reality star says of her toned body. "I know what it needs to run well, and that doesn't include drugs, alcohol, or cigarettes."

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In addition to regular runs, cycling classes and personal training sessions, Bensimon stays fit by riding horses. "Gripping the animal with my thighs to stay on is the ultimate lower-body workout," she says.

The Real Housewives star watches her diet six days a week, allowing herself to splurge on Sunday -- "or what I like to call Funday."

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Bensimon tells Shape she's passing down her healthy eating habits to her two daughters, Teddy, 13, and Sea, 11 (with photographer ex-husband Gilles Bensimon).

"They're learning to make meals that are delicious and healthy," Bensimon says.

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