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Jessica Simpson is taking her post-baby weight loss efforts seriously -- and it's paying off, big time.

On Sunday, the mom to Maxwell headed to LAX to catch a flight to NYC. Before boarding her flight, Simpson, 32, looked comfy, casual and slimmer than ever in a black tunic and formfitting black pants.

PHOTOS: Jessica Simpson's body evolution

The "Fashion Star" mentor is slated to make her first public appearance since giving birth four months ago during a chat with Katie Couric on the TV host's new talk show Monday.

Last week, Simpson opened up to Us Weekly about her success using Weight Watchers so far.

"I'm 10 pounds away from my pre-baby size," said the singer/designer, who got up to 170 pounds while pregnant.

PHOTOS: Jessica Simpson's curve-hugging looks

In addition to adhering to the popular point-based eating plan, Simpson said she's working out four times a week with celeb trainer Harley Pasternak.

"Her waist is going in, and her thighs are getting smaller," Pasternak said of his A-list client's progress so far.

PHOTOS: Jessica Simpson's most outrageous moments

Though she still has a little bit of work to do before she's back to her goal weight, Simpson is confident she can make it happen. Now that she's a mom, she told Us, "I believe I can do anything!"

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