Thomas McIntyre weighed more than 31 stone and had a waist measuring 74 inches.
The 43-year-old was on medication for a range of health concerns such as high blood pressure and breathing problems, and admitted his weight was a constant worry.
"I was the typical jolly fat bloke, always making fun of myself before anyone else had the chance to do it," he said.
"Deep down though I'd reached the point where I thought about my mortality all the time and the more I worried the more I ate, to comfort myself I suppose. It was a vicious cycle."
The Celtic fan, who is six foot tall, had been overweight for more than two decades and grew steadily in size since giving up playing football in his early 20s.
Now everything's easier and I'm so much happier. If we are lucky enough to have children, I'll be the active dad I always wanted to be and that's really important to me.
He was so worried about his weight in the run up to his wedding that he secretly purchased a bigger, back-up suit - in size 8XL.
Thomas also discovered that he was too big to get through the turnstile at a sports grounds when, to his embarrassment, he became trapped while dozens of supporters watched on.
He continued: "My weight felt like a huge burden when I married my beautiful wife Claire.
"She's always loved me for me but getting a suit was difficult and I felt awful in it. Getting stuck in a turnstile when I went to Partick Thistle's ground wasn't much fun either, after that I had to go in through the disabled gate every time I went to a football game."
Thomas, a fresh food manager at Dunnes Stores, set about losing weight in February 2012 by changing to healthier eating habits and taking up regular exercise.
His average breakfast menu had previously consisted of four large sausage rolls, packet of crisps, chocolate bar and cola - now he eats grilled lean bacon, eggs fried in low calorie cooking spray, mushrooms and baked beans with two small slices of toast.
Thomas managed to lose 17st 8lb, going from 31st to 13st 6lb and a size 8XL to a medium.
His achievement was recognised when he was awarded the title of Slimming World Man of the Year 2013 at the Ritz Hotel in London.
But he says the biggest change is in how he feels about himself - his confidence is soaring, he's learning to drive for the first time and is even hoping to start a family.
"I feel like life passed me by for years so I'm determined to live it to the full now," said Thomas.
"I can fit through the turnstiles when I go to the football now so there's no embarrassment there, in fact, that's the only downside to my weight loss because I have to queue with everyone else!"