No 'extreme' diets: Jessica Simpson's trainer reveals how she lost 100 pounds

Jessica Simpson lost 100 pounds by making sure she got her steps in every day — at least 14,000 of them, to be exact.

The 39-year-old mother of three has been focused on making small lifestyle changes to safely lose weight after she welcomed daughter Birdie Mae in March 2019.

Her longtime trainer, Harley Pasternak, said Simpson started out by walking 6,000 steps per day.

"It had to be more than just getting back from her baby weight, but how do I keep whatever I am doing now forever. That's why we are not a big fan of doing any extreme diet or radical forms of exercise," he told E! News in an exclusive interview.

Simpson eventually worked her way up to at least 14,000 steps per day. While she first showed off her results last September, Simpson has been able to keep up the routine. She appeared strong and happy in an Instagram post on Wednesday.

"Woke up before all 3 kiddos to get my steps in and spend time with me, myself, and I," she wrote. "Move move move for your own mental health."

Simpson also focused on eating three healthy, protein-packed meals a day and two snacks, such as almonds. Instead of cheat days, she would have several cheat meals throughout the week, Pasternak said, that way she didn't feel deprived of her favorite foods.

Pasternak advised Simpson on one overlooked component of weight loss: getting enough sleep. He said the fashion mogul aimed for seven hours a night.

"So many people undervalue the importance of sleep in weight loss and weight management," he said.