Former forklift driver Patrick Broadbent, at 39 stone (250 kilograms), is battling for his life as he awaits vital surgery to save his life.
According to a report in the Mirror newspaper, Broadbent knew he needed help when experts used a truck weighbridge to find out how heavy he was.
He weighed 13 stone (83 kilograms) until he was 20, but gained seven stone in less than two years following an accident at work that left him with epilepsy.
"I was hit on the back of the head by a pile of pallets that fell over. I don't remember much about the accident. I was in hospital for 10 days. When I returned to work I started having blackouts and had to stop work," he said.
He was placed on a drug called Tegratol to curb the effects of his illness but he was devastated by the news and slumped into a depression. Broadbent blames the drug for his weight gain.
"I suppose if I lived in America I'd hardly get a second glance - but I live in Derry and it's a very different matter," he said.
Patrick has been assessed by a world authority on obesity and gastric bypasses, and now awaits life-saving bypass surgery next year.