Nuala McMahon has undergone an incredible transformation after the embarrassing incident at the Florida theme park three years ago.
Publicly humiliated and ashamed about her weight in front of her family and strangers, the 29-year-old vowed to do something about it.
Having just suffered the devastating loss of her beloved grandfather, Nuala, from North Belfast, said she felt lost, Belfast Live reports.
Recalling the horrifying moment she was called a 'big rider' during a family holiday to Florida, Nuala says she was humiliated.
She said: "Before I started to lose weight three years ago, I was in Florida and I was so big, I couldn't fit on the rides. They even have a modified seat in two rows of the rides and I didn't fit it, isn't that awful?
"It was terrible for me, it more or less ruined the holiday.
"Then there was another really embarrassing moment, they have tester seats outside the rides so I tried it and I fitted, so I was all excited and we got into the queue and got on the seat and buckled the harness over me, but there was a light at the end of the row that was red and wasn't changing to green.
Now she looks amazing and is down to a size 14
"So they automatically came over and looked at me and said look we need to push this seat in more, but I was saying, 'look you can't push it anymore I can't breathe'.
"So she motioned to lift the seat up and she said, 'We have a big rider here, she doesn't fit', and I was like, 'No, it's fine', and she pushed it back down again and it turned out the light was nothing to do with me.
"It was an empty seat on one of the other rows that hadn't been clicked in properly."
Nuala added: "But they automatically looked at me and they said that a couple of times, 'Oh we have a big rider here'.
"I was mortified, it was in front of all my family I was so embarrassed and you're worried about them being embarrassed and then the crowd of people, you just feel so disgusted with yourself too and you're thinking how did I let myself get like this?
"I remember just feeling really sad, like my friends were going out buying new outfits and I was trying to recycle clothes because I didn't want to go shopping and I just stopped going out, I lost interest."
But she was done with making excuses and made it her mission to lose weight.
Nuala was humiliated at Disney
A size 26 approaching 28, the 29-year-old says she hated the thought of exercise, but one gym class helped her on her way to saving her life.
She said: "I knew that I was bigger but not to the extent that I actually was.
"You sort of make excuses and you don't see it, and it's not that my clothes were getting too tight, it was my mummy was shrinking them in the tumble dryer, those kinds of things.
"After my grandad died, Christmas came around and you know we all eat more at Christmas but I was walking and trying to talk at the same time one day and I couldn't, I was getting pains in my chest and just walking to the corner shop was knocking the puff out of me, so I thought right I need to do something.
"So my partner Johnny, he had joined the gym and he had been on at me for ages to come down but I had no interest.
"But one night I went down to pick him up and his aunt was there and she invited me to a gym class with her, and I didn't really know her well enough to say, 'no, away on with ye', so we exchanged numbers and I had no intention of going, but God love her she hounded me and I went.
"It was a Body Combat class on the Saturday and I couldn't move for about a week after it, it was awful but it was brilliant at the same time and that was it, I just stuck at it."
After loving her first gym class, Nuala was determined to stick with it and began making small changes to her diet.
Now she is happy and healthy with her size
She said: "At the start changing my diet wasn't too dramatic, now years ago I would have drank five litres of Coke per day, and I came off that and when I did that I lost half a stone. I still drink Coke now but it's a tin or two at the weekend as a treat and that's it.
"After that then I cut out bread and just reduced my portion sizes, at the start I was still having a lasagne but I wasn't having the chips or bread with it, instead having it with a load of salad.
"Then it was just other small changes like swapping white rice for brown, grilling everything and eating lots of fish, eggs and chicken, just making small changes and then having a cheat at the weekend.
"For the first while as well I stopped drinking, not that I was a big drinker anyway but when I have a drink I want to have something to eat too, not just while I'm drinking but the day after it too, to make yourself feel better so I cut out drink for a while."
At first, Nuala said she didn't really notice her body changing, but a shopping trip soon changed that perception.
She explained: "It was only when I bought a pair of jeans in Florida and they didn't fit, and I put them away and one day I came across the jeans and tried them on and they were too big - it was then I started to notice changes in my body.
"The first time I went shopping again I was in Dublin Christmas shopping and I went into River Island for the first time and picked up a pair of jeans and my daddy told me to try them on, and I kept saying, 'No this is River Island they won't fit', but they did, and they were a size 16.
"I couldn't believe it, I cried I was so happy and I bought three pairs. I went to Primark a few weeks ago for the first time ever as well, I had never been able to shop in there before."
The 29-year-old blogs about her weight loss online
The 29-year-old also started her own Facebook page 'From Phat to Phabulous' to help keep a track of her weight loss, which has attracted thousands of supporters.
Nuala explained: "I'm between a [size] 14 and 16 now but I'm not done yet.
"I still have weight to lose, I'm still going through it but I think with my page on Facebook people can relate because I'm still trying to get to my goal.
"My sisters encouraged me to set up the page on Facebook, at the start it was just an online diary for me and then people started to respond and like it so I kept it up.
"People have been so lovely and encouraging. Although I'm not finished, at the minute it's more about keeping fit and healthy and it's helped my mental health as well.
She admits there are ups and downs
"What I post on my page is real, there's no sh**, it's all real life. I don't try and sugar coat it and pretend that everything is great, I will tell people that I'm hungry and that I'm annoyed and that some days it is really hard.
"I'm sick of reading all these things about losing weight, people saying it's brilliant and all these happy, smiley people, it's not all great, there are times when you're not smiling and it's hard, it's been the most challenging thing I have ever done but it has saved my life."
Nuala said she was shocked to hear she was a 'ticking time bomb' before she started her weight loss journey.
She added: "I lost four stone on my own and then the weight loss started to slow down and I couldn't figure it out, I was going to the gym twice a day.
"So I spoke to a Personal Trainer and he told me I actually wasn't eating enough, so I started training with him for a while and lost another stone and then learned myself what I should be eating.
"I was chatting to him one day and he told me at the start he didn't want to put me off, but he told me if I hadn't of started to try and lose the weight when I did I was a ticking time bomb to die.
"He said not to be dramatic but you were a ticking time bomb for a heart attack or a stroke so hearing that was unbelievable."
You can continue to follow Nuala's progress on her page here.