Sarah Wass said she wanted to "stick two fingers up" to people who made cruel jibes about her size after she tipped the scales at 24st 10lb.
The 30-year-old became a recluse and would avoid social situations for fear of being judged by strangers.
After an off-the-cuff comment from her mum that she would not find any clothes to fit her if she got any bigger, Sarah was spurred into action and lost an astonishing 12 stone in just 18 months.
The mother-of-one ditched takeaways, started cooking healthy meals and took up aqua fit twice a week, joined a gym and started walking three miles a day.
After noticing the weight drop at a rapid rate through her new strict regime, the shop assistant set herself a goal of losing 12 stone in time for her 30th birthday.
When she hit the target, she treated herself to a new fashionable dress she never would have dreamed of wearing before - and arranged a night out she would previously have shied away from.
Sarah, who now weights a trim 12st 11, went from a "tight" size 28 to a "comfortable" size 14 - and is now so slim she can fit both legs into one leg of a pair of shorts she used to wear for bed when at her biggest.
She said: "I wanted to put two fingers up to people who had called me fat and made jokes about me.
"I've been called a 'fat cow' by strangers when I've been out and you feel people looking at you, judging you.
"It got to the point where I didn't like to go out. I just used to stay in my own little bubble at home. I would avoid going anywhere if I could."
Speaking about the struggle with her weight, Sarah said: "I have been big all my life. I had such a bad diet and I didn't exercise. I used to struggle just walking around and I would get out of breath really easily.
"People I know would make jokes about my weight. It was only banter and they didn't mean anything nasty by it, but it gets to you.
"You try to laugh it off and make out it doesn't, but it does. It got to me a lot.
"My mum commented a few times, she wasn't being nasty, but she got me a coat that was size 26/28 and she said 'if you get any bigger, you're not going to be able to find anything to fit you'.
"It was a horrible red coat and it made me feel like a big red road tomato, but it was the only coat in my size.
"I had to wear horrible clothes I didn't like just because they fit me. Now I can get stuff I actually like.
"I bought two new dresses for my birthday - I would never have been able to wear a dress before. I would have been in leggings and a baggy t-shirt all the time."
Sarah, who would previously gorge on takeaways three times a week, now cooks all her meals from scratch at home.
Her daughter Katelyn, five, is also benefiting from her new healthy lifestyle.
She added: "I don't even think about takeaways now. When the leaflets come through the door, I put them straight in the bin.
"People think I have had weight loss surgery and don't recognise me. Friends I haven't seen for a while will double take to see if it's me.
"My health is through the roof. I'm energetic and I can do a lot more with my daughter.
"Before I would be stuck on the sofa and not go out, not do anything and Katelyn would suffer and be stuck inside too.
"Now we go for days out and we go to the park. After the weight started to come off, I thought I can't go back.
"All my hard work would have been pointless.
"It's unbelievable when I look back at pictures now, I don't feel like it's me."