How Jessica Simpson shed 100 pounds

You can do exactly what super successful mogul and celebrity Jessica Simpson did to lose weight — and it won’t cost you a dime.

According to her personal trainer, Simpson walked off 100 pounds.

Her trainer Harley Pasternak told “E! News” he worked with Simpson’s doctor to design a plan for her after she gave birth to her third child, daughter Birdie Mae, in March.

Simpson shared on social media that she had weighed 240 pounds while pregnant.

“6 months. 100 pounds down (Yes, I tipped the scales at 240),” Simpson wrote in the caption on an Instagram photo showing off her weight loss. “My first trip away from #BIRDIEMAE and emotional for many reasons, but so proud to feel like myself again. Even when it felt impossible, I chose to work harder.”

Pasternak said they worked on making small, sustainable changes to help her lose the weight.

“It had to be more than just getting back from her baby weight, but how do I keep whatever I am doing now forever,” he said. “That’s why we are not a big fan of doing any extreme diet or radical forms of exercise.”

That included coming up with healthy alternatives to her favorite foods and getting her up to walking 14,000 steps a day, Pasternak said.

The celebrity trainer has been working with Simpson for 12 years and said she started out slow after recovering from childbirth and got her steps in via activities that included family walks and hitting the treadmill.

It helped, Pasternak said, that the star was really committed to feeling and looking better.

“We were kind of just getting in shape between kids and now it was sort of OK, I want to look fierce again and look great, confident and energized and I want to do it in a sustainable way,” he said. “That was her main goal.”