According to the Guinness Book of Records - WORLD'S LARGEST WAIST
Jan 15 2002, 9:15 PM
Walter Hudson (USA) had a 9 ft. 11 in. waist (size 119 inches) in 1987. His typical daily snack was 12 doughnuts, 10 bags of potato chips, 2 giant pizzas, and half a cake!
That would make the diameter just under 38 inches (does not sound that big, there must be somebody bigger out there)