A study published on Monday in The Lancet Diabetes and Endocrinology journal reports that weight loss surgery, such as the fitting of a gastric band, can reduce a person’s risk of developing type 2 diabetes by up to 80%. This confirms findings from a previous study conducted in Sweden but expands what we know about the effectiveness of the various types of surgical procedures used in the UK. The study highlights the possibility of using obesity surgery as a means of preventing type 2 diabetes in those who are at highest risk of the disease – a possibility that has attracted a great deal of media attention and controversy.

Weight loss surgery is currently a treatment option for people who are considered extremely obese, defined as a body mass index (BMI) of 40 or higher. People who are obese with a BMI of between 35 and 39, and also have additional existing health risks such as type 2 diabetes, are also eligible. Statistics from the UK show that 2.4% of the adult population is extremely obese, with women of lower income status at highest risk. The consequences associated with extreme obesity are well documented, including increased risks for chronic diseases including cardiovascular disease, some cancers, and particularly type 2 diabetes. Approximately 2.6 million people in the UK have been diagnosed with type 2 diabetes, which is projected to increase to 4 million people by 2025. In addition, about a half a million people have diabetes but have not yet been diagnosed. Approximately 10% of the NHS budget is spent treating diabetes, with additional costs resulting from human suffering and absenteeism from work.

Contrary to provocative news headlines and popular belief, not just anyone is eligible to receive obesity surgery. Eligibility is determined not only by a person’s BMI but also by a history of multiple unsuccessful attempts to lose excess weight through lifestyle and/or medication, their risk of chronic diseases, and their physical and psychological readiness to go through surgery and cope with the major, sustained lifestyle changes they must adhere to following surgery. Owing to commissioning limitations, many people who are eligible for surgery do not receive it.

The need to prevent type 2 diabetes, and to successfully treat it once a person is diagnosed, is unequivocal. However, what is controversial is how we should go about doing this in the most effective and cost-effective way. Research shows weight loss to be the most effective way to prevent and treat type 2 diabetes. But achieving weight loss through lifestyle changes is not always easy and is difficult to sustain. Obesity surgery can reverse type 2 diabetes in those who have it – at least in the short term – and this recently published study shows it can also prevent type 2 diabetes. However, we know that some patients may regain weight in the longer term following surgery, and type 2 diabetes can recur in patients over time even if they have maintained their weight loss.

We are still missing an important piece of the type 2 diabetes treatment puzzle. What is needed is a randomised controlled trial conducted in the UK examining the long-term effectiveness and cost-effectiveness of obesity surgery compared with lifestyle intervention on preventing diabetes in those at high risk. A study such as this should include not only those with extreme obesity but also people who are identified as obese with a BMI between
30 and 34.

The current state of the evidence is such that we do not have a definitive answer as to the long-term effectiveness and cost-effectiveness of using obesity surgery to treat type 2 diabetes within a national healthcare system. Although results from existing research suggest obesity surgery may be a promising treatment option for type 2 diabetes, the cost and risks associated with the surgery need to be examined alongside those of lifestyle intervention approaches before we can be confident that obesity surgery is our most effective and cost-effective option to treat type 2 diabetes across the full range of obesity levels in adults.

Professor Janice L Thompson
Professor of Public Health Nutrition and Exercise, University of Birmingham