Keith Martin (1970 - March 2014), one of the World's heaviest living people, was famous at one point for being the UK’s heaviest man, weighing approximately 980 lbs at his peak. Keith Martin was given a gastric bypass operation by the NHS, and had lost over 50% of his body weight. Early life Keith Martin’s mother had died of pneumonia when he was only 16. Martin had used junk food as a comfort from this traumatic life event, which was the cause of his extreme weight gain. Death Martin (much like his mother) had developed pneumonia, and died as a result from it.