Credit: Jon Furniss/; Anwar Hussein/

Kate Middleton's middle has gotten a lot of attention since she and her husband Prince William tied the knot one year ago. But lately, it's her on-trend style choices -- not pregnancy rumors -- that has her fans fixated on her waist.

No stranger to sporting chic and sophisticated outfits, the Duchess, 30, has shown off her slim figure in two column outfits adorned with a peplum waist. So why is the royal so into the trend?

"Kate is very lean with a strong shoulder line, so the peplum works beautifully on her lanky frame to create shape and balance," Sam Saboura, style expert and Extreme Makeover alum, tells Us Weekly. "The peplum highlights Kate's waist and adds curve to her narrow hips."

Adding that fashionistas are migrating toward the demure detail because it helps create the illusion of an hourglass-shape figure, Saboura says that the look is also about adding a soft feminine touch to an otherwise buttoned-up and conservative look, like Kate's emerald L.K. Bennett skirt suit she wore March 8.

If you find yourself coveting the style that Kate and several fashion-forward Hollywood actresses like Emma Stone, Jennifer Aniston and Michelle Williams have tried out, Saboura advises to be conservative about your choices, unless you want to look like Lady Gaga!

"The key to a perfect peplum is soft structure," he says. "Look for jersey fabrics with a bit of stretch that will give you the right amount of volume and drape without overwhelming your frame. If you are long-waisted, the peplum should sit a little higher on your cage. If you are short-waisted you can try a skirt with a peplum that sits closer to your hips to help elongate your torso."