The first large-scale study on the impact of bariatric surgery -- which includes gastric bypasses and gastric bands--, also found that it helps prevent or eliminate premature death, disease and disability.
The study by the National Bariatric Surgery Registry (NBSR) found that while cases of type 2 diabetes halved among obese patients just a year after the surgery, the average patient shed nearly 60 per cent of their excess body weight, the Daily Mail reported.
The research, which is an analysis of data from more than 8,700 operations carried out in the UK, found that 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 after 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, it claimed.
There was also improvement on all associated diseases.
The NBSR said the cost of bariatric surgery is recouped within three years as obesity-associated costs are eliminated.
"This data shows that not only is UK bariatric surgery safe, but it successfully treats a whole range of diseases --including the rapid resolution of diabetes," said Dr Alberic Fiennes, a bariatric surgeon and the chairman of the NBSR data committee.
He said: "An approach that limits treatment to a fraction of those who would benefit is one which the NHS will rue in years to come as these patients become an unsustainable burden on the health service.
"Prevention strategy alone has proved ineffective. There are at least two generations of morbidly obese patients who are now presenting with diabetes, stroke, heart disease and cancer for whom preventative measures are utterly irrelevant.
"The numbers are increasing - these people need to be treated."
Gastric bands involve surgery under general anaesthesia, which carries the risk of complications including infection and on rare occasions life-threatening blood clots.
NHS statistics show the death rate associated with band insertion to be about one in 200 shortly after operations, and one in 100 shortly after a gastric bypass.