While she never had a problem fitting into her clothes, it was when Mrs O'Brien was pregnant with her son 11 years ago that she put on 50 per cent of her body weight — weighing in at 91kgs — the heaviest she has ever been.
"It was embarrassing having people touch your tummy and ask if you're having twins or even triplets," she said. "But I was in denial. I kept telling myself it was normal and as soon as he popped out, I'll go back to how I was."
At her heaviest, mother-of-two Kerrie O'Brien weighed 91 kilos. She went from a size 18 to a size 8 in 15 months. Photo / Supplied
In between having her son and getting pregnant with her daughter two years later, Mrs O'Brien continued to go to the gym, but said the weight wasn't coming off as quick as she hoped.
"When I got pregnant with my daughter I went back up to 90kg. I was about 86kg just before that, so not much lighter."
For the next nine years, a now size 8 Mrs O'Brien had tried nearly every diet, even cutting out sugar and upping her cardio game to five times a week — but nothing changed.
"I wasn't losing any weight. I was putting in all this effort and I really had to resign myself to the fact I was old and had kids late in life and for that reason, nothing was working," she told news.com.au.
Living on the Gold Coast, you would often find Mrs O'Brien comfortably rocking a swimsuit on the beach.
"That was before kids," she said.
"Since earlier this year I actually hadn't been in our pool — not even in front of my own family did ever want to wear bathers, let alone in public.
She trains up to six times a week in her bedroom using The Healthy Mummy app. Photo / Supplied
"It's sad to think all the things you miss out on doing with your kids because you worry about how you look."
However, all that changed just two years ago, when her friend introduced her to The Healthy Mummy, a parenting health site exclusively for mums.
"I remember buying a dress for my 47th birthday and I was so excited to wear it. Even though I had to wrap myself in layers of spandex control underwear to fit into it … but I thought I looked pretty good. Until I saw the photos afterwards. I was horrified," Mrs O'Brien said.
"I had a good friend who would come over my place often. She had lost 10kgs in six months — she too was never overweight but her transformation was dramatically noticeable."
Even though her friend added her to The Healthy Mummy support group, Mrs O'Brien had lost all hope.
"It was depressing because I'd see all these other women my age who were thin and it would make me wonder what I was doing wrong.
Her advice - 'it's never too late to start'. Photo / Supplied
"I needed someone to help me and point out what I was doing wrong — and that's what The Healthy Mummy did for me. I learned that there were actually things in my approach that were wrong such as not eating enough or hitting the calories I needed to fire my metabolism."
In 15 months, Mrs O'Brien went from a size 18 to a size 6 to 8 — all without having to go to the gym.
"I exercise 6-7 times a week and it's all done in my bedroom — bedroom bikini body — it's funny but it's true," she said. "You don't need a gym to do their exercises, all you need is a fitness matt and you have someone (video) telling you what you need to do. It's like having someone physically with you."
Her diet now consists of curry's, stir-frys and pasta. "All the dishes people think you can't have when trying to lose weight."
For 12 years, Mrs O'Brien also suffered from heart arrhythmia — irregular heartbeats — which was another motivation for her to shed the kilos.
"The good news is that since I have lost the weight I haven't had an episode at all."
After having struggled with her weight after kids for nearly 10 years, Mrs O'Brien said she has never felt happier and more confident.
Here she is looking fit and fabulous just a year short of her 50th birthday. Photo / Supplied
"I was still carrying an extra 26kgs post pregnancy and it took its toll on my body, my health and my confidence for the years after in my 40s," she said, adding, "I didn't want to turn 50 feeling overweight with heart problems as I am aware those things get worse."
She said that while it may have taken her a while to get to where she is now, nothing can replace how good she feels about herself.
"It's never ever too late ladies. Even when you think it is. Better to arrive later than never."
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