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This NIHR-funded study found that very obese adults who had weight-loss surgery were 80% less likely to develop type 2 diabetes within 7 years than similar obese adults who did not have weight-loss surgery. The study data came from a large UK-wide database of general practices which was representative of the UK population. The treatment and monitoring of people in the study was realistic and typical of current routine clinical practice, increasing its applicability to the UK.

Why was this study needed?

Obesity and type 2 diabetes are both common in the UK and rates are rising. Obesity has more than doubled in the last 25 years to over 25% of adults, while over 3 million people in the UK are currently diagnosed with type 2 diabetes. Diabetes accounts for about 10% of the NHS budget. Obesity is the main risk factor for type 2 diabetes, and losing weight can reduce the risk of type 2 diabetes. Tackling obesity and preventing diabetes is a priority commitment in the NHS England 2015/2016 business plan.

Weight-loss surgery, also called bariatric surgery, covers a range of surgical techniques to help people who are very obese lose weight. In 2013, a major study in Sweden found that bariatric surgery reduced the risk of type 2 diabetes by 78%. However, because the study was started over 20 years ago, it was not clear how relevant these findings would be to current UK practice. This new study investigated whether weight-loss surgery for people with obesity can reduce their chance of developing type 2 diabetes. Importantly, the researchers selected people being treated in routine NHS clinical settings rather than just specialist units, meaning that the results of the study are likely to be relevant across the UK.

What did this study do?

Using a UK-wide database of medical information from more than 680 general practices, the study traced two groups of obese adults (defined as a BMI of at least 30 kg/m2) without diabetes . One group of 2,176 people had weight-loss surgery, while the other, control group, (2,176 people) did not. The groups were matched for possible confounding factors such as BMI, age and sex. Information was also collected on history of coronary heart disease, stroke, depression, blood pressure, total cholesterol, smoking status, and on treatment for high blood pressure or high cholesterol. The main outcome was new onset of type 2 diabetes. People were followed-up for 7 years.

What did it find?

  • For obese people (60% of whom were very obese, BMI of 40 kg/m2or more) weight-loss surgery reduced the risk of developing type 2 diabetes by 80% (adjusted Hazard Ratio 0.20, 95% Confidence Interval 0.13 to 0.30), over the 7 years of follow up.
  • By the end of the 7 year follow up about 4% of people who had weight-loss surgery developed diabetes compared with 16% in the group not having surgery. A difference of 12%.

Differences in the characteristics and treatment of the surgical and non-surgical groups could have influenced the results. For example, people in the non-surgical group did not receive standard non-surgical weight-loss treatment, had fewer records of health monitoring, were less likely to have depression, and had more data missing from their records than those having weight-loss surgery. This may have introduced some bias. However, the reduction of diabetes risk was so large that the result is unlikely to have been entirely due to these factors.

What does current guidance say on this issue?

A 2012 NICE guideline recommends weight loss interventions for people with obesity to reduce the risk of developing type 2 diabetes. Dietary advice, lifestyle change and medication are offered first, aiming to achieve specific weight loss goals. If weight loss goals are not met, people can be referred to specialist weight management services, including weight-loss surgery. Based on BMI criteria and the NICE guidelines, the majority of the participants in this study would have been eligible for weight-loss surgery.

What are the implications?

This systematic review confirms that weight-loss surgery is very effective at reducing people’s risk of developing type 2 diabetes. Although surgery is more expensive than non-surgical interventions, it is very cost-effective over the patient’s lifetime. However, despite its efficacy, access to this surgery in the UK is currently limited and varies from region to region.

NHS England recommends that they should retain responsibility for the commissioning of weight-loss surgery. However, they plan to transfer all but the most complex weight-loss surgery to clinical commissioning groups once the groups are shown to be functioning well.

NICE advises that surgery for obesity should only be undertaken by a multidisciplinary team that can provide a suitably experienced surgeon and surgical team, pre and post-operative assessments, manage comorbidities and provide psychological support. Relevant data on surgery and outcomes is being collected by the National Bariatric Surgery Registry.


Booth H, Khan O, Prevost T, et al. Incidence of type 2 diabetes after bariatric surgery: population-based matched cohort study. Lancet Diabetes Endocrinol 2014 2;12:963-968. This project was funded by the National Institute for Health Research HS&DR Programme (project number (12/5005/12).


Colquitt JL, Pickett K, Loveman E, Frampton GK. Surgery for weight loss in adults. Cochrane Database Syst Rev. 2014;8:CD003641Diabetes UK. Diabetes: Facts and Stats. London: Diabetes UK; 2014

Diabetes UK. The cost of diabetes. London: Diabetes UK; 2014

NHS England. Joint report on commissioning obesity services published. London: NHS England; 2014

NICE Pathways. Surgery for obese adults. London: National Institute for Health and Care Excellence; 2014

NICE. Obesity: identification, assessment and management of overweight and obesity in children, young people and adults. NICE CG189. London: National Institute for Health and Care Excellence; 2014

NICE. Preventing type 2 diabetes: risk identification and interventions for individuals at high risk. NICE PH38. London: National Institute for Health and Care Excellence; 2012

Picot J, Jones J, Colquitt JL, et al. The clinical effectiveness and cost-effectiveness of bariatric (weight loss) surgery for obesity: a systematic review and economic evaluation. Health Technol Assess. 2009;13(41):1-190, 215-357, iii-iv

Sjöström L. Review of the key results from the Swedish Obese Subjects (SOS) trial - a prospective controlled intervention study of bariatric surgery. J Intern Med. 2013 Mar;273(3):219-34

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre

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The most common types of bariatric surgery in the NHS are gastric banding, gastric bypass and sleeve gastrectomy. Gastric banding binds the top of the stomach, effectively cutting it in two. The reduced size of the stomach means that it takes less food to make the patient feel full. Sleeve gastrectomy works in a similar fashion, but actually removes part of the stomach. Gastric binding is reversible, while sleeve gastrectomy is not. Gastric bypass is similar to gastric binding in that it divides the stomach in two, but it also creates a bypass around some of the rest of the intestines meaning fewer calories are absorbed. Gastric banding was the most common technique in the present study, used in almost half of participants (49%), followed by gastric bypass (37%).


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