A mother-of-three who died two weeks after weight-loss surgery had been told by her doctor that her chances of dying were one in 2,000.
Clare White was also told that having a gastric band fitted around her stomach could so dramatically improve her health she may no longer need insulin for her diabetes, an inquest heard.
She was 'keen' to have the operation after exhausting all other means of slimming down during a 14-year battle with her weight, which had risen to nearly 19 stone.
But the 37-year-old, of Sinfin, Derbyshire, had a cardiac arrest and died after the operation at Royal Derby Hospital.
A post-mortem investigation found that she died of a blood clot in her right lung caused by diabetes-related heart problems.
The post-mortem found that the clot was also contributed to by an infection.
Surgeon Paul Leeder, who carried out the weight-loss operation, said he believed this infection was caused by the gastric band irritating her stomach.
He told Derby and South Derbyshire Coroner’s Court that Mrs White was 'keen' to have the operation and was told it carried a one-in-100 chance of serious complications and a one-in-2,000 risk of death.
He said: 'This type of operation is not cosmetic surgery.
'Most people of Mrs White’s weight lose a decade of life expectancy, and I believe her life expectancy would have been significantly less than that due to her diabetes, which she had for 16 years.
'Although the operation does carry a degree of risk, these risks were far outweighed by the risks of her staying as she was.
'Many diabetic patients come off insulin and go into remission following this operation.
'That was our main aim and I’m very sorry we weren’t able to do that.'
He said Mrs White weighed 119kg (18st 10lb) at her pre-operative assessment.
She was assessed as being at moderate risk of developing a blood clot and measures were taken to try and prevent this, such as blood-thinning injections.
The operation was carried out on September 21, 2010, and was 'entirely straightforward', Mr Leeder said.
But husband Craig White told the court that his wife was in pain after leaving hospital and kept vomiting her painkillers.
He said: 'She was not the Clare I knew. She was normally quite a strong-willed woman but she was quite withdrawn and in immense pain.'
On September 29 he took her to the casualty department and she was readmitted to hospital.
Mr Leeder was on annual leave, so Mrs White was cared for by his colleagues.
They discovered she had an infection, so they removed her gastric band to try and prevent further problems.
Mr Leeder said one possible cause of infection following gastric band surgery was a hole in the wall of the stomach or bowel which had been created during the operation and his colleagues suspected that was the case with Mrs White.
However, pathologist Dr Ivan Robinson found no sign of any hole when he carried out the post-mortem.
Mr Leeder said he believed that the band irritating the outside of the stomach caused the infection.
The witnesses agreed that Mrs White’s treatment would have remained the same even if this had been diagnosed while she was alive.
Dr Robinson concluded from his post-mortem that the main cause of the blood clot was the fact that Mrs White’s diabetes had affected her heart so her blood was not circulating properly.
But he said the infection following the operation, as well as further complications from her diabetes, also played a part.
The pathologist said: 'The operation has contributed to her death but I can’t say whether by 20 or 50 or 80 per cent.'
He said the infection would have made her heart condition worse, and would have affected the functioning of her other major organs and increased the risk of blood clots.
Dr Robinson added that the infection had been successfully treated by the time of her death, on October 4, 2010.
Deputy assistant coroner Paul McCandless told the court he had heard all the evidence he intended to take.
He is set to deliver his verdict on Friday morning.