Manuel Uribe had slimmed down to about 867 pounds (394 kilograms), well below his then-record peak weight of 1,230 pounds (560 kilograms), which was certified in 2006 as a Guinness World Record.
Uribe had been confined to his bed in Monterrey for years.
The official said Uribe had been taken to the hospital because of an abnormal heartbeat.
He had to be taken to the hospital with a crane by emergency and civil defence workers.
Doctors have not yet certified the cause of death. He was also believed to have suffered from liver problems.
Uribe married Claudia Solis in 2008, and the wedding was one of the few times he left his home in recent years.