See Jessica Simpson's sexy gown change for the White House Correspondent's Dinner afterparty

It’s no secret that Jessica Simpson has been turning it out on the red carpet lately. And on Saturday at the White House Correspondents’ Dinner, the star had her first glam gown moment since giving birth to her 10-month-old son Ace Knute, commanding everyone’s attention (and generating weight loss buzz once again) in a floral Carolina Herrera gown.

Jessica Simpson White House Correspondents' Dinner

Evan Agostini/Invision/AP

Since Simpson has been working so hard for her toned physique, we don’t blame her for wanting to show it off in more than one dress. (Plus, it was a date night away from the kids for the designer and her fiancé Eric Johnson.) She switched into a sexy, strapless black gown with a thigh-high slit for a USA Today following the dinner. “After the prez it’s the after party #whcd @usatoday,” Simpson captioned the below photo on Instagram.

The secret behind her new body? A source close to the star told PEOPLE that the Weight Watchers spokeswoman finds balance in eating right and doing exercise that’s fun for her (along with her 45-minute trainer sessions with Harley Pasternak three days a week).

“She likes walking in her neighborhood and people often see her doing that,” the insider shared. “She really enjoys the workouts. [Because] she loves it, she’s consistent. It’s the one constant in her life that she’s always done no matter whats happening.”

And her pending nuptials are the push she needs to stay fit. “We are very close to sending out our invites,” Simpson told USA Today during the weekend festivities.

What do you think of the star’s red carpet style? Which dress do you like best? Share your thoughts below.

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–Brittany Talarico