Pop star-turned-TV personality Jessica Simpson is set to wow fans next week when she debuts her new post-baby body on TV.

The "Irresistible" singer blossomed and ballooned when she fell pregnant with baby Maxwell, but she has lost a staggering 40 pounds in the four months since she became a first-time mom.

And now Simpson is set for a big post-pregnancy reveal in front of millions on the premiere episode of U.S. newswoman Katie Couric's new talk show on September 10.

Life & Style magazine reports Simpson shed the baby weight thanks to breast-feeding, marathon gym sessions and a personalized, no-starve WeightWatchers plan.

A source tells the publication, "Jess has been doing a lot of work on herself and she'll gradually be showing her weightloss through WeightWatchers commercials over the next few months."

Simpson reportedly filmed her first commercial for the weightloss company on August 16.

However, she's still struggling to lose the last few pounds to reach her goal weight. She tells USA Today, "My body is not bouncing back like a supermodel. I'm just your everyday woman who is trying to feel good and be healthy for her daughter, her fiance and herself."