An expansion of weight loss surgery in England is being proposed to tackle an epidemic of type 2 diabetes.
New draft guidelines from the National Institute of Health and Care Excellence (NICE) aim to reduce debilitating complications, which are a huge drain on NHS resources.
Diabetes UK estimates 850,000 people could be eligible for surgery, but NICE expects it to be tens of thousands.
Type 2 diabetes is closely linked to lifestyle and obesity.
A mounting body of evidence suggests a gastric bypass improves symptoms in around 60% of patients.
Around a tenth of NHS budgets is spent on diabetes.
The surgery can cost up to £15,000 and the move by NICE has raised concerns that the NHS will not be able to afford the treatment, even if there are savings in the longer term.
Current guidance says surgery is an option for people with a BMI above 35 who have other health conditions.
Around 8,000 people a year are currently receiving the treatment.
The update in guidance strengthens the focus on those with type 2 diabetes.
It explicitly states that people who have been diagnosed in the past decade and have a BMI over 35 should be assessed for surgery.
The guidelines also suggests doctors should consider those with a BMI of 30 or more on a case-by-case basis.
It means a man who is 6ft (1.83m) tall and weighs 18st 6lb (117kg) would be sent for an assessment, and doctors would be expected to consider sending a 5ft 5in (1.65m) woman, weighing 12st 10lb (80.7kg), as well.
Diabetes UK says around 460,000 people will meet the criteria for an automatic assessment under the guidance.
But the total jumps nearer to 850,000 when those with a BMI of 30 are also considered, it says.