Two million people could qualify for obesity surgery under radical new NHS guidelines.
The health watchdog NICE says new evidence shows the procedure pays for itself in two to three years and doctors should no longer see it as a last resort.
Anybody with a body mass index of 30 or more who has recently been diagnosed with type 2 diabetes, and has tried a compulsory weight-loss programme, would be eligible under the new guidance.
But the rigorous assessment and a reluctance to undergo major surgery is likely to result in just 5,000 more people a year having the operation, rising to 15,000 a year in future.
Currently 6,500 people a year have the 6,000 procedure on the NHS.
The guidelines are expected to cost the NHS 27m at first, but two-thirds of patients are able to stop their diabetes medication, saving between 1,000 and 2,000 a year.
Dr Rachel Batterham, head of obesity and bariatric services at University College London Hospitals NHS Trust, said surgery has an immediate effect on the way the body handles sugar, effectively curing diabetes.
She told Sky News: “This is surgery that alters how the body works.
“It is safe and effective, it saves lives, saves money and we really need to get that message across.”
One in 20 people has type 2 diabetes, which is related to lifestyle.
It causes 24,000 premature deaths a year, mostly from heart disease and strokes.
It also results in 100 patients a week having limb amputations.
But Diabetes UK said far more needs to be done to prevent the disease.
Barbara Young, the charity’s chief executive, said: “It makes no sense that the NHS is currently spending more on bariatric surgery than it is on preventative measures to stop people from getting type 2 diabetes in the first place.
“All surgery carries risks and so, as the NICE guidance makes clear, people should only be offered surgery if attempts to lose weight through healthy eating and physical activity have already been tried and not worked.”