They discovered that the average patient sheds nearly 60% of their body weight in the year following surgery, from an analysis of data from more than 8,700 operations carried out in the NHS and private sector.

It found two thirds of severely obese patients had three or more associated diseases by the time they reach surgery. A third have high blood pressure, over a quarter have diabetes and nearly a fifth have high cholesterol.

Patients who had a 12-month follow-up examination following surgery had lost some 58 per cent of excess weight, while cases of type 2 diabetes fell by 50 per cent.

After two years, 86 per cent of those affected by diabetes prior to surgery showed no signs of the disease. There was also improvement on all associated diseases.

The study which looked at operations including gastric bypasses and gastric bands – said the costs were recouped within three years as obesity-associated costs are eliminated.