Kate Middleton is rapidly becoming as much a fitness icon as she is already a fashion queen, if those slender legs and beautifully toned hands in designer gowns are any indication.

"Kate does an hour's workout every morning using the gym ball and dumbbells, which includes some core exercises like squats, sit-ups and arm curls," a royal insider told Now magazine. Marie Claire reports the same thing - adding the Duchess is reportedly a huge fan of the gym balls and a big sports enthusiast, with rowing, biking and canoeing at the top of her list.

An earlier IBTimes UK report spoke of a secret dietary regime - the Dukan - which focuses on starting with protein before alternating between that and green vegetables. This is to be followed with a regular diet and one day a week dedicated, once again, to proteins.

Meanwhile, the Duchess' younger sister isn't far behind.

Pippa Middleton was spotted at a friend's wedding recently and reportedly looked lovely and fit in a pink dress. Incidentally, a report in USA Today noted that the raspberry-coloured Issa wrap was the same dress (but different colour) to the one her sister wore to announce her engagement to Prince William in 2010.

While Kate's secret is the gym ball, Pippa's, apparently, is Pilates. Marie Claire reports weekly classes and workouts have helped her increase her core strength and posture.

"As someone who is always 'on the go', Pilates has been a wonderful escape from my busy lifestyle in London. Whether it's 7am in the morning or 7pm at night I always leave feeling calm, refreshed and invigorated. Over the past few months I have noticed a huge difference in my core strength and posture and couldn't recommend Margot Campbell (her trainer) more highly as a Pilate instructor. From breathing techniques, muscle toning to overall flexibility and relaxation, my Pilates sessions have become something of a weekly necessity that keeps me fit, happy and energised," Pippa said.

Britain's Prince William and his then fiancee Kate Middleton smile during a visit to St. Andrews University in Fife.Reuters.
Britain's Catherine, Duchess of Cambridge arrives for the 'Our Greatest Team Rises' event to celebrate TeamGB and ParalympicsGB at the Royal Albert Hall, in central London May 11, 2012.Reuters
Kate Middleton in a cream full length gownTwitter