Hundreds of thousands of people with type 2 diabetes could be offered weight-loss surgery on the NHS.
New draft guidance from the National Institute of Health and Care Excellence (Nice) suggests that obese people with the condition should be assessed for bariatric surgery - such as having a gastric band fitted to reduce the size of the stomach or a gastric bypass, where the digestive system is re-routed past most of the stomach.
At present weight loss surgery is given to patients on the NHS to those who are morbidly obese with a body mass index (BMI) score of over 40 or to those who have a BMI over 35 and who have another serious health condition - such as type 2 diabetes.
But now Nice is suggesting that people with a BMI score of 30 to 35 should be considered for an assessment for weight-loss operations on the NHS if they have been diagnosed within the last 10 years.
This could mean hundreds of thousands more patients could be considered for treatment.
Data from the National Diabetes Audit show that around 71% of people with type 2 diabetes were diagnosed in the last decade. And around half (47%) of those with the condition have got a BMI over 30. If these figures were extrapolated this could mean that as many as 800,000 could be considered for this type of surgery on the NHS.
The draft guideline also recommends that people who have undergone bariatric surgery on the NHS should have a "follow up care package" for at least two years after their operation.
"Obesity rates have nearly doubled over the last 10 years and continue to rise, making obesity and overweight a major issue for the health service in the UK," said Professor Mark Baker, director of the Centre for Clinical Practice at Nice.
"Since the publication of the existing guidance in 2006, more information has become available on how best to tackle the issue.
"Updated evidence suggests people who are obese and have been recently diagnosed with type 2 diabetes may benefit from weight loss surgery.
"More than half of people who undergo surgery have more control over their diabetes following surgery and are less likely to have diabetes related illness; in some cases surgery can even reverse the diagnosis."
Commenting on the draft recommendations, Simon O'Neill, director of health intelligence at charity Diabetes UK, said: "For most people, losing weight can be very difficult. For some, as well as a healthy diet and physical activity, additional treatments include medication and surgery.
"Although studies have shown that bariatric surgery can help with weight loss and have a positive effect on blood glucose levels, it must be remembered that any surgery carries serious risks. Bariatric surgery should only be considered as a last resort if serious attempts to lose weight have been unsuccessful and if the person is obese.
"Bariatric surgery can lead to dramatic weight loss, which in turn may result in a reduction in people taking their type 2 diabetes medication and even in some people needing no medication at all. This does not mean, however, that type 2 diabetes has been cured.
"These people will still need to eat a healthy balanced diet and be physically active to manage their diabetes."
In the UK around 2.9 million people have diabetes, with around 90% of cases being type 2. There are also thought to be around 850,000 people with undiagnosed diabetes.
The draft Nice guidance on obesity, which updates guidance published in 2006, also states that doctors should be "selective" about recommending very-low calorie diets to obese people trying to lose weight.
Prof Baker added: "Very-low-calorie diets have grown in popularity in recent years, so we now have more evidence to consider how well they work, if the weight loss can be sustained and the safety concerns, than we did in 2006.
"The new draft guidance now recommends that they should not be used routinely for people who are obese, only those who have who have a clinical need to lose weight quickly, such as before joint replacement surgery."
The draft guideline has been issued for consultation.
Diabetes UK's chief executive Baroness Young said: "I don't think that bariatric surgery should be an option for 800,000 people. The more important thing is that we actually make sure that people who begin to develop overweight and head for obesity get effective intervention long before they fall within the criteria that would justify bariatric surgery."
She told BBC Radio 4's Today programme surgery could be the right option "for a very small number" but added: "Give me the 5,000 quid that you would spend on an operation and put it into a weight reduction programme earlier on and we could win."
James Halstead, a bariatric surgeon at Leeds Nuffield hospital, told Today: "The recent data has shown that the actual number of NHS-funded bariatric surgical procedures in the UK is falling, not rising.
"It's falling from such an incredibly low baseline level of around 8,000 cases annually that the idea that one can deal with 900,000 people in the next three years with this avenue alone is nonsensical."