"The remaining people demonstrate big improvements of blood sugar control and can drastically reduce their dependence on insulin or other medication.

"In many patients, blood sugar levels go back to normal within days, long before declines in fat levels or weight."

The treatments stem from a new view of the causes of diabetes, a condition in which there is too much glucose in the blood.

Diabetes has previously been blamed on the pancreas not secreting enough insulin, the hormone that controls glucose levels - but Rubino and his colleagues believe the gut is the key player.

Andrea Midmer, 59, a nurse, took part in the trial, in which a plastic liner or "endobarrier" was fitted into her stomach to stop the walls of her upper gut coming into contact with the food she ate.