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.

"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."

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."

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.