The 44-year-old woman, from the town of Santhià in north-west Italy, died after a “sleeve gastrectomy”, Il Mattino said.
The surgery is used to tackle extreme cases of obesity and involved reducing the stomach by up to 75 percent.
When the patient began suffering pain after the operation, she was transferred from the Istituto Clinico Beato Matteo to the emergency room of nearby Vigevano hospital.
Following a series of medical complications, she died around 48 hours after being admitted to hospital, Il Mattino reported.
An autopsy is due to be carried out to determine the precise cause of death.