Over two million people in England are eligible for surgery to treat obesity, according to new research.

However, fewer than 7000 patients underwent these procedures in 2011.

Carrying out more bariatric surgery procedures would help to reduce obesity-related ill health, the study authors from Imperial College London said, but the NHS may need to invest in more resources to meet demand.

Bariatric surgery – a set of surgical procedures performed on obese people to decrease their stomach size – can greatly reduce the likelihood of death from obesity-related diseases such as type 2 diabetes, stroke or coronary heart disease.

Despite clear guidelines outlining who can undergo such surgery with the NHS, and evidence that these procedures are cost-effective in the long run, less than one per cent of those eligible have weight loss surgery each year. The researchers say this raises questions about why more procedures are not currently being carried out.

One possible reason is that patients and GPs lack awareness of the surgical procedures and potential benefits. Commitment to lifestyle intervention is also an important barrier, as patients must be willing to enter a full life-changing programme involving intensive management in a specialist obesity service and commitment to long-term follow-up.

The research, published in JRSM Open, found that 5.4 per cent of the population could be entitled to bariatric surgery.

Those eligible are more likely to be women, be retired, have no formal education and be from a lower socio-economic status than the general population.

Dr Sonia Saxena, from the Department of Primary Care and Public Health at Imperial College London, said: “Performing more operations could be very good for the population in terms of improving patient health. You could cut down on a number of very severe conditions and extend life expectancy in patients who are likely to suffer significant problems as a result of their obesity.”

But the research, funded by the Higher Education Funding Council for England and the National Institute for Health Research, revealed that the capacity of health services to meet this demand is limited.

“The NHS would be overwhelmed because there isn’t the resource to actually carry out this number of operations,” Dr Saxena added.

“If everyone who was eligible came forward there would most likely be a restriction because of funding and resource allocation at the local level.”

To calculate the number of eligible people, the researchers used population data from the 2006 Health Survey for England, a nationally representative household survey carried out every year by the government to plan health services and make policy decisions.

They combined them with guidelines from the 2006 UK National Institute for Health and Clinical Excellence (NICE). The NICE guidelines assess eligibility for bariatric surgery according to a person’s body mass index (BMI), a measure of body shape based on mass and height. People with a BMI exceeding 40, or those with a BMI between 35 and 40 and suffering from one or more obesity-related diseases, are eligible for bariatric surgery with the NHS.

But Dr Saxena explained that eligibility based on NICE guidelines alone is not the end of the story. “We know from our previous work in the United States that fewer bariatric surgery operations are carried out in disadvantaged groups who are most in need of the operation because of a lack of health coverage. But everyone who is eligible is entitled to the operation in the NHS and there is a huge potential health gain. Some of those who are eligible may not be aware they could benefit or willing to make the lifestyle changes for a successful procedure.”

Reference: A. Ahmad et al. 'Eligibility for bariatric surgery among adults in England: analysis of a national cross-sectional survey.' JRSM Open January 2014 vol. 5 no. 1 doi: 10.1177/2042533313512479