Pippa Middleton, the 31-year-old sister of the Duchess of Cambridge, is opening up about the healthy lifestyle she follows for keep her famous physique. And unlike other celebrity diets, this one sounds realistic. 

"I grew up with the belief that good health is about moderation in all things, so I'll be celebrating healthy living through exercise, a balanced diet and a little of the naughty stuff sprinkled in — I'm talking chocolate, crisps, and the occasional glass of wine," she writes in a new column for Britain's Waitrose Weekend magazine.

While Pippa extols the benefits of consistent exercise, she's quick to dismiss fad diets. 

"I've never done Dukan, attempted Atkins or exercised religiously seven days a week, but I do believe in making healthy choices — keeping refined carbs such as white bread and pasta to a minimum, and sticking to sensible portion sizes," she writes. 

As for her workout routine, Pippa appears to keep it practical, saying she tries to fit in three to five exercise sessions per week. If it works for someone who regularly competes in grueling charity marathons (including a recent crazy 3,000-mile bike race across the U.S.), it can work for you. 

"Be it a 30-minute run, an hour’s walk or a good game of tennis, it boosts my mood and energy, and helps me sleep and digest better," she writes. "So I make it a priority, whatever the weather or my work schedule."

While Pippa's popularity initially stemmed from her debut during her sister's nuptials to Prince William, she's since been building a name of herself in both print and media. According to sources, she's reportedly close to signing a deal with NBC's "Today" morning show to become a correspondent on all things health and lifestyle. 

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Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

Pippa Middleton's healthy lifestyle secret? Moderation
31-year-old says healthy choices and not fad diets are the keys to maintaining a fit lifestyle.