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Weight loss surgery cures half of patients with type-2 diabetes, for at least five years, a study suggests.

The trial, on 60 people, published in the Lancet, found none of those with type 2 had been cured by medication and diet alone.

The surgery improves symptoms both through weight loss and by changing the way the gut functions.

Experts said the results were "remarkable" and that too few people were getting access to the surgery.

The team, at King's College London and the Universita Cattolica in Rome, compared standard drug therapy with surgery to rewire the digestive tract.

The operations reduced the size of the stomach and left less of the intestines exposed to food.

Prof Francesco Rubino, who operated on the patients, told the BBC News website: "Surgery is able to produce prolonged remission in 50% of cases, patients get to levels of blood sugar that is non-diabetes for five years.

"However, 80% who had surgery were able to maintain 'optimal control' [of blood sugar] despite only taking one drug or nothing at all."

While some of those patients still had type-2 diabetes, they were easily keeping their sugar levels to recommended levels.

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The patients who had surgery were also less likely to have heart problems, a common side-effect of uncontrolled diabetes, and reported improved quality of life.

Prof Rubino added: "Treating surgically, rather than medical therapy, appears more cost-effective, as there is less use of medication."

The results were better two years after surgery. However, some patients relapsed in the past three years.

The surgeons say there still needs to be continual monitoring of blood sugar levels even after the operation.

Drs Dimitri Pournaras and Carel le Roux, from Imperial College London, said diabetes was "the plague of the 21st Century" and that the results were "remarkable".

They added: "Surgery for diabetes seems to be safe, effective in terms of glycaemic [sugar] control, and is now associated with reduced complications of diabetes.

"The ultimate question is whether diabetes surgery is associated with reduced mortality."

However they said surgery needed to "become more available because only a few patients who will benefit are currently offered this potentially life-saving option".

New rules in the UK have been introduced that should increase the number of patients being offered weight loss surgery.