The mum-of-five tweeted: "Why is everyone sooo obsessed with being sooo skinny? It's good to feel healthy and fit but not just to be skinny."
Katie's tweet prompted some fans to point out that Katie herself is a slim size eight, just months after giving birth to her baby daughter Bunny.
But Katie replied: "I've always been small I'm just sick of everyone thinking being really skinny looks good it should be about being healthy."
Former glamour model Katie, 34, gave birth to fifth child Bunny in August 2014 and quickly snapped back into shape, however she insisted it was to do with her natural figure and not because she was dieting and over-exercising.
She also pointed out she hadn't gained weight during her pregnancy.
Meanwhile, in other Katie news, she recently gushed about how she couldn't wait to renew her wedding vows with husband Kieran Hayler, despite him cheating on her last year.
The star was left devastated after learning Kieran had slept with two of her friends while she was pregnant with their son Jett, now one.
But she chose to forgive him and tweeted this week she was "so proud" of the progress he had made through his therapy sessions, where a therapist told him he had a compulsive addiction to chasing illicit thrills.
Katie hasn't revealed yet when the wedding vows will take place, although a source told Reveal the day will be one to remember, with celebrity guests, extravagant dresses and the release of white doves to symbolise Katie and Kieran's love.
"Katie's in the throes of planning a really expensive vow renewal event and she's even sourcing theme ideas and picking a guest list," said the insider.
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