Kelly Foulds, 38, says she was 'addicted' to the bottles of pop, a habit which had led her to be overweight since her teens.
At the age of seven, she was diagnosed with Bell's Palsy, a condition which causes the left side of her face to droop, and adds that this was one of the triggers which caused her to start comfort eating.
'When I was 13, I started drinking Sprite and I loved the taste,' Kelly told The Mirror. 'If I was feeling fed up, I'd buy a couple of bottles from the shop. The sugar gave me a pick-me-up.'
'I ate chips every lunchtime at school and although my parents cooked healthy stews or roast dinners, I ate huge portions.'
Kelly's struggles with her weight continued through her time at university and into adulthood, with her weight eventually rising to 27 stone.
'I scoffed cakes, pizzas and drank fizzy drinks like they were water,' she admits. 'Despite being morbidly obese I still didn't care enough to do anything about it.'
'Finding clothes to fit was a nightmare and I lived in tracksuit bottoms and baggy tops. When I graduated I was so big I had to wear elasticated trousers and a baggy shirt while most of the other girls wore dresses.'
'I had another bout of Bell's palsy and didn't recover fully which really hit my confidence. I suffered with facial spasms and was in pain. Food made me feel better so I ate for comfort.'
'I used to go to the kebab shop in my lunch hour. I'd wash it down with two bottles of pop. Calling at the shop on my way home to buy more pop was as normal as buying eggs and milk.'
It was only after paying a visit to the doctor complaining of back pain that Kelly realised how out of control her diet had become.
'The doctor wanted to know about my diet and I told him how much fizzy pop I was drinking,' she said. 'He explained how bad it was for my teeth, liver and kidneys, but he was more concerned about my weight.'
On his advice, Kelly started to cut down on the sugary drinks, but it wasn't until she joined Weight Watchers in January 2010 that her transformation truly began.
'I learnt about portion control and how important it is to have a healthy, balanced diet. My whole attitude towards food changed and I started to wean myself off the fizzy drinks.'
'The first day was really hard because I felt bad tempered and anxious. I also had terrible headaches and insomnia. It was strange not having a bottle of Sprite in my hand. But as the weeks went on I started to feel better and I became addicted to losing weight instead.'
In just three months, Kelly managed to ditch the fizzy drinks for good, and set about changing her eating habits too - a process which saw her gradually lose more than half her body weight.
She now has scrambled eggs or porridge for breakfast, followed by a chicken salad and a small jacket potato for lunch. Dinner is chicken with vegetables, and if she fancies a snack, she'll have Weight Watchers crisps or fruit - or the occasional small diet Sprite as a treat.
'It hasn't been easy but even though I've been left with excess skin around my middle, it's a small price to pay,' she concluded. 'I've even taken up running for the first time.'
'I'd never worn a dress in my life and now I've got five size 14s. It's an amazing feeling seeing them hanging in my wardrobe.'
'I feel great and love going shopping for new outfits. I still have an occasional chocolate bar and I stick to vodka or brandy – but with diet coke – and I've never felt better.'