Jessica Simpson is ready to show the world her incredible weight loss!

Just five weeks after giving birth to son Ace, Life & Style can exclusively reveal that the fashion mogul will flaunt her slimmer post-baby body in photos for a new Weight Watchers campaign launching later this year.

"She has already lost a good amount of weight and looks great in the pictures!" a source tells Life & Style.

Casually dressed in layered T-shirts and wearing minimal makeup, the insider dishes, "The shirts are snug on Jessica and she looks so thin in the photos. It's quite remarkable for how recently she gave birth."

Inside Jessica Simpson's Nursey For Baby Ace

And the company can't wait to show off the Fashion Star mentor's new look.

"Weight Watchers is so excited to the put the pics out there once the campaign officially launches," the source adds. "Jessica bounced back a lot quicker after giving birth to Ace than she did after having [15-month-old daughter] Maxwell — and it's clear after this photo shoot!"

As Life & Style reports in this week's issue, the blonde bombshell has already lost 25 pounds thanks to a clean diet. Plus, unlike her first pregnancy, where she gained 70 pounds, the 33-year-old stayed slimmer this time around.

"She is eating well," a pal of Jessica's tells Life & Style. “It’s all down to portion control and cutting back on fried foods, plus restricting the amount of desserts she eats."