There have been several recorded, including one that died in 1983 who passed the 1,400 pound mark. His name was Jon Brower Minnoch from Bainbridge, Washington State. This following information involves a more recent one in Mexico:
"Health officials said Manuel Uribe weighed 1,235 pounds when he made a desperate plea for help on national television in January. "
"Manuel Uribe sits on his bed at home in Monterrey, Mexico in a January 17, 2006 file photo. Uribe, who at 550kg (1,212 pounds) is possibly the heaviest person in the world, hopes to travel to Italy for a life-saving operation to shed weight." 
Wikipedia's List Of Most Obese people