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.

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.

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

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.

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.