AceShowbiz -

Jessica Simpson was one of the guests that visited Katie Couric on the premiere of her new talk show. The new mom showed off her post-baby body in an all-black ensemble, and opened up about her struggle to shed her fat after giving birth to her baby girl, Maxwell Drew.

"During pregnancy, I didn't really think about it," she said. "I thought my doctors were telling me that it was just a lot of water and whenever my water broke my whole entire stomach would go down but that did not happen. All the weight did not come out with the baby!"

"I've had to really stay focused on my diet and really concentrate on what I'm putting in my body," the fiancee of Eric Johnson (II) continued. "[It's] definitely a challenge," the singer confessed. "I put on more baby weight than I was planning on putting on."

Jessica, who was tapped as new spokesperson for Weight Watchers after delivering her first child, weighed 170 pounds when she posed nude for its April cover. After a hard work that included healthy diet and workout routine, she lost 40 pounds since giving birth.

In a new ad for the weight-loss company, the mother of one said, "There's a lot of pressure to lose weight, but I'm not a supermodel, I'm just Jessica trying to eat real food in a real world and really just wanna be healthy for my daughter." Instead of flaunting her body, she just sat in front of the camera while making her statement.

Last June, Jessica denied she's getting any pressure from the weight-loss company to lose her post-baby fat. "Just so everyone knows...Weight Watchers hasn't put ANY pressure on me!" she insisted, "I'm trying to be as healthy as I can be for myself and I feel great!"

When appearing on "Katie" recently, she emphasized her statement. "I really have to separate myself from the world's expectations and really just look inside myself and be healthy with myself," she gushed.