Jessica Simpson, who has been flaunting her new svelte silhouette in recent weeks, rocked the red carpet with her fiancé Eric Johnson at the White House Correspondents' Dinner in D.C. But one of her best accessories was definitely her new skinny waist.

Jessica showed off a tiny waist in a flowered Carolina Herrera gown that she wore with Neil Lane earrings and bracelet. Eric wore Ralph Lauren and posed side-by-side with his future wife.

Sources told E! News that Jessica's weight-loss secret has a lot to do with her children, especially Maxi, who is almost two-years-old. The mom has shed the pounds by chasing after her brood and playing on the swings in their backyard. She is also fond of taking walks, gardening and other outdoor activities that keep her moving.

Jessica recently talked to Good Morning America about the importance of living healthy instead of opting for quick-fixes and fad diets.

"I really do feel this need to be the best role model for my children," she said in January. "I want [Maxwell] to look up to me and want to be like me...I don't want to give her any false perception of what is real and what's important."

Whatever you're doing Jessica, keep doing it! You look amazing!

She has been open about struggling with her weight in the past.

But mother-of-two Jessica Simpson was more than happy to show off her new toned, shapely legs on a night out with her fiance Eric Johnson in LA on Friday night.

The 33-year-old, who is the face of Weight Watchers in the US, revealed in February how she had lost 50 pounds whilst following the diet giant's weight plan.

Since giving birth to son Ace in June 2013, the fashion designer has worked hard to get her slender shape back as a spokeswoman for Weight Watchers.

'This body made two amazing little human beings,' she said in a February Weight Watchers commercial.

'I love this body and what it's capable of-no matter what size. But this version,' she said.

Then gesturing to her svelte physique, 'feels really good. My body, like my life, is a work in progress, but I'm getting there, with Weight Watchers.'