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