The illness used to be called ‘mature onset’ diabetes because it was associated with the middle-aged and elderly, but in the past 15 years it has been seen in children and in September a three year old girl was diagnosed with the condition, the youngest patient ever seen.

Traditionally, Type 2 diabetes is seen as a progressive condition which is controlled by diet initially then tablets, but which may eventually require insulin injections.

The new study is the first to suggest that keeping weight down can cure patients.

Researchers were able to spot the link between fat in the pancreas and diabetes because of a new MRI scanning technique which allowed them to accurately test levels of fatty deposits in the organ. It showed that fat levels decreased by 1.2 per cent over eight weeks in diabetic patients. During the eight weeks the patients were asked to limit the calorie intake to 1200 kcal a day, around half of recommended levels.

A control group of non-diabetic obese patients saw no change in the level of fat in their pancreas demonstrating that the increase in fat in the pancreas is specific to people who develop Type 2 diabetes.

Naveed Sattar, professor of Metabolic Medicine at the University of Glasgow said: "This is a big deal because it shows that weight gain is triggering diabetes and that people who lose enough weight can be diabetes free and come off insulin.