Jessica Simpson's trainer reveals how she shed 45kg in six months

The mum of three has shared her staggering results on social media. Photo / Getty Images

Jessica Simpson's personal trainer has revealed how she lost a staggering 45kg after giving birth to her third child six months ago.

Harley Pasternak says the mum's transformation is down to a new "holistic post-baby lifestyle," and that she only worked out for 45 minutes a day.

"My mantra is you get lean in life, and strong in the gym. So the majority of the weight loss actually came from everything she did outside of the gym, and then everything in the gym is about toning and tightening," he told People.

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NYC Ladies’ Night ✨

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"The difference between this and the other times was that she worked out, yes, but her transformation was more about what she did on her own time."

The former singer and actress took to Instagram to show off her impressive results.

"6 months. 100 pounds down (Yes, I tipped the scales at 240)," she wrote.

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6 months. 100 pounds down (Yes, I tipped the scales at 240 😜) 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. 💚

A post shared by Jessica Simpson (@jessicasimpson) on Sep 24, 2019 at 10:00am PDT

"My first trip away from #BIRDIEMAE and emotional for many reasons, but so proud to feel like myself again," Simpson said. "Even when it felt impossible, I chose to work harder."

Pasternak has trained Simpson for the past 12 years and helped her get back in shape after the birth of her other two children, Maxwell, 7 and Ace, 6.

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Jess-tation

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He does however admit the third time was the hardest - after Simpson hit 108kg and suffered sciatic pain, bronchitis and swollen feet during her most recent pregnancy.

"This is sort of the aggregate of being pregnant non-stop for a decade, and so we had a little more of a challenge between this and the other ones."