A new medical study has said that the NHS could save millions of pounds a year by offering more weight-loss surgery for obese patients.

About one million people in England meet recommended criteria for so-called bariatric surgery, but only 3,600 NHS weight-loss operations were carried out last year.

Obesity and related medical conditions directly cost the NHS £4.3 billion a year, while the impact on the wider economy runs into millions.

The Office of Health Economics estimates that £1.3 billion would be saved within three years, if a quarter of those eligible underwent surgery.

Savings of between £35 million and £150 million could also be made in welfare payments as people return to work, according to the study, titled “Shedding The Pounds”.

John Black, president of the Royal College of Surgeons, which commissioned the report along with the National Obesity Forum, described the figures as “simply staggering”.

“The NHS cannot afford to ignore the mounting evidence that shows that bariatric surgery, for those patients where all other treatments have failed, is not only proven to be successful but also hugely cost effective,” he said.

The report was funded by health firms Allergan and Covidien, which make medical equipment used in weight-loss surgery.

Almost a quarter of adults in England were obese in 2008 – a figure expected to double by 2050.

The National Institute for Health and Clinical Excellence (NICE) says people with a body mass index (BMI) of more than 40 – or between 35 and 40 if they also have a condition such as diabetes or high blood pressure – are eligible for surgery.

Liberal Democrat Health Minister Paul Burstow said:

“Our ambition is to encourage healthier lifestyles and reduce the need for this type of treatment.”

“As part of the Change4Life movement, we are encouraging people to make simple changes, such as eating more fruit and veg, cutting down on fatty foods and being more active.

“Our public health white paper later this year will set out plans to help people lead healthier lifestyles in more detail.

“Whether to prescribe drugs or recommend surgery is rightly a clinical decision. Independent guidance on obesity from Nice recommends that drugs and surgery should always be a last resort – a better diet and more exercise should be tried first.

“It is up to individual trusts to commission a range of services to meet their local community’s needs.”