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Jessica Simpson's Personal Trainer Reveals Exactly How She Lost 100 Pounds Six Months Postpartum

Losing 100 pounds in six months is no easy feat, but with the help of her trainer, Harley Pasternak, Jessica Simpson is back to her pre-baby body.

Curious as to what her fitness secrets are? Keep reading to find out exactly how she did it!

Jessica Simpson put in serious werk to lose 100 pounds.

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The mom of three, who welcomed her most recent child, Birdie Mae, in March says that she's "so proud" to feel like herself again.

Her trainer, Harley Pasternak, spoke to "E!" recently about the challenges Jessica was up against to lose the weight.

That's because she weighed in at 240 pounds and had a goal of losing 100 pounds in six months.

"We had our work cut out for us and perhaps more so on this baby than the others," he said.

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To ensure everything was safe, Pasternak put together a plan that worked in coordination with Jessica's doctor.

The goal was to create long-lasting habits that the singer could carry on long after her goal weight was reached.

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"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."

Instead of having Jessica do super intense workouts right off the bat, they started off slow with a goal of walking 14,000 steps a day.

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She just had a baby at that point, so they didn't want to move too fast.

But Jessica had to build up to 14,000.

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She got a break while she recovered from having the baby.

However, after that, it was time for Jess to hit the streets. Pasternak started her off on a more achievable 6,000 steps a day.

As for her diet, Pasternak said that he helped Simpson find healthier alternatives of her favorite foods.

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In general, though, she would eat three meals a day, along with two snacks.

Each meal consisted heavily of lean proteins and lots of veggies.

An invention of Pasternak helped, too.

While Jess was working up a sweat, Harley was putting his brain to work.

He created Sweetkick, which is a mint that helps curb sugar cravings. Um, I'll take 12, thanks.

An example of snacks would be parmesan green beans and a handful of almonds.

Sounds delish!

And instead of "cheat days," Jessica would have "cheat meals."

She wasn't denied her fave foods, either!

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He never intended to "rob" Jess of her favorite things, but to make slow changes that incorporated healthier proteins and veggies.

Doing this kept things "more balanced and sustainable."

"You don't have to have all of your indulges in one day. It tends to be a little extreme if you do that," Pasternak said.

Another one of their goals was making sure that the new healthy habits fit into her daily routine.

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This meant having her go on family walks and having her multitask TV and phone calls while on the treadmill.

They didn't want her doing anything "too difficult, painful, hard or arduous."

Unplugging from technology was another major habit to adopt.

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She would unplug from technology one hour before bed.

"So many people undervalue the importance of sleep in weightless and weight management," Pasternak explained.

Once these healthy habits were in place and Jessica got approval from her doctor, Pasternak leveled up her workouts.

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"We slowly ramped those up; we started really easy and slowly increased them," he explained.

"We started with doing a full-body workout, one set of each exercise, not really doing too much intensity per body part and gradually increasing the volume and intensity."

Another key aspect of her journey involved her family.

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To meet those step goals Harley set for her, Jessica started adding family walks to her daily routine.

The whole gang would head out and work up a sweat while hitting those 6,000 and 14,000 step goals.

"Focusing on a few muscle groups per day. Different muscles each day of the week."

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He said that Simpson had a great attitude during the whole process, despite having to check in daily.

For example, he tracked what she ate, her step count, and got screenshots from her Fitbit.

They were in constant communication.

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Daily emails helped ensure that Jessica kept Harley up to date on everything involving her get healthy journey.

When she wasn't outside, she was making use of her personal time.

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Since she was at home, Jessica could take care of business and her help at the same time.

She walked on a treadmill while watching TV or answering calls.

Another reason why Jessica's attitude was so great is because she's worked with Pasternak for 12 years.

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He's now helped her lose the baby weight with all of her kids!

As a result, she trusts him and the process.

Lastly, Jessica made it clear that she's committed to making health and wellness a part of her forever lifestyle.

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"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. That was her main goal."

More importantly, she hopes that her new healthy habits will set a good example for her kids.

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"She is feeling like she did before she had kid. In control of everything and such a great attitude of not beating herself up if she doesn't eat perfectly every day so it's a very helpful perspective."

Now, she's snatched for the gods.

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Queen of being healthy and posing next to private jets!

And the future looks bright.

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She's working with Macy's on her fashion line, she's releasing a book next year with Harper Collins, and she appears regularly on the Home Shopping Network.

That's one busy mama!