The mum-of-five posted a photo of herself running with a large backpack on her Instagram story.
Katie, 41, captioned the photo: “Day 1 of 6 weeks fitness challenge for the new healthy KP.”
It seems a battle of the bodies is underway between the former partners as Kieran, 32, posted a shirtless photo on his Instagram the same day.
He wrote: “With hard work and determination you can reach your goals!”
The reality star seems to be committed to her fitness goals, as she is splashing out on huge renovations for her “mucky mansion” – despite being so in debt she might lose her home.
Part of the renovations in her Sussex home include a gym, beauty studio and horse exercise arena.
A source previously said to The Sun Online: “Katie’s planning this huge showbiz comeback and thinks she’ll be a millionaire by the end of the year, so spending money on the house is actually an investment.
“She’s building a beauty studio where she can film YouTube videos as part of her new vlogging career, and a small gym that Kris can work out of – something she always promised Kieran but didn’t do.”
She’s since broken up with Kris Boyson and moved toyboy Charles Drury into the house.
Since their messy divorce last year, the pair – who have kids Jett, 6, and Bunny, 5, together – have been making jibes at each other about their appearance.
On an episode of Katie’s show My Crazy Life last year, she says to Kieran in an argument: “You’re still fat.”
He replies with: “Well you still wear too much make-up. What are those eyebrows? You look like Charlie Chaplin.”
The dad-of-two said previously that his ex-wife “treating him like s**t” brought back memories of his experience with bullies at school.
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Kieran has jumped back on the fitness wagon and has already launched his personal training career with his first celebrity client since his divorce with Katie.
Katie previously promised Kieran that he could train people in a gym in the family home, but she eventually banned him after he cheated on her with the nanny.
Now the former stripper is going to be training reality star Danielle Mason.
A source told The Sun Online: “Danielle Mason and Kieran met a the launch of Buzz Talent at Fest in Camden last week and Danielle commented on how well Kieran was looking.
“He’s lost two stone since splitting up from Katie and all her fat shaming. Danielle loves Katie Price – she’s her idol – so asked Kieran if he could get her into shape like Katie.”
Katie Price screams ‘I don’t have money’ at ex Kieran Hayler on My Crazy Life
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