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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.

Surgery is a cost-effective method of weight loss for severely and morbidly obese people. This study of general practice data compared health costs and outcomes for people with severe or morbid obesity who underwent surgery and those who did not. Surgery was associated with a reduced chance of developing diabetes and an increased chance of remission in people with diabetes. It was more cost-effective – using NHS thresholds – for morbidly obese people who had diabetes, than for those without diabetes.

Weight loss surgery either reduces the amount of food people can consume or the amount of energy they can absorb from food. A quarter of UK adults are obese, with 3.6% of women and 1.8% of men severely or morbidly obese. These numbers are projected to rise, so addressing obesity is a key public health issue.

This study provides further evidence to support the implementation of NICE recommendations. However, commissioners will need to consider the upfront costs for the large number of people who could potentially benefit and balance these against other demands on budgets and how to fund services in the lower “tiers” of weight management (see Definitions).

Why was this study needed?

Around a quarter of UK adults are obese, with a body mass index (BMI) of 30 or more. Obesity is linked to increased risk of health problems such as stroke, diabetes, cancer and high blood pressure. These conditions affect quality of life and increase health costs. Costs and benefits of obesity treatments rise in line with BMI, hence the rationale for undertaking this study to assess whether the added benefits are worth the added costs (the value to the NHS). Life expectancy is also reduced by up to 8 to 10 years in people who are morbidly obese (BMI 40 or more).

Surgery can help obese people to lose weight. This involves reducing the size of the stomach to limit food intake or bypassing sections of the digestive system to reduce the amount of energy absorbed from food.

In the UK there is a gap between the number of people who are eligible for weight loss surgery and those receiving it. For example, The National Obesity Observatory recently reported that there were fewer than 7000 inpatient bariatric surgical procedures performed in England in 2009/10, but more than 1 million patients are potentially eligible based on current guidance. This study set out to calculate the cost-effectiveness (or value to the NHS) of increasing access to weight loss surgery for morbidly and severely overweight people.

What did this study do?

This study used electronic general practice health records to gather data about weight loss surgery and people’s on-going health. It compared 3045 people who were morbidly (BMI 40 Kg/m2 or more) or severely obese (BMI 35 to 39 Kg/m2) and had received weight loss surgery with 176,495 ‘matched’ obese people who had not had surgery.

An economic model combined this data with that from systematic reviews of the effectiveness of surgery, with the costs to calculate the cost effectiveness of surgery. Benefits were measured in Quality-Adjusted Life Years (QALYs). The various health states and costs for people in these states were compared. These included states such as diabetes, heart disease, cancer and depression. Scenarios were compared for people who had and hadn’t received surgery, in age, gender and BMI categories.

What did it find?

  • Weight loss surgery was associated with a reduced likelihood of obese people developing type 2 diabetes of about 80%. Among people who received surgery, 5.7 per 1000 per year developed diabetes (95% confidence interval [CI] 4.2 to 7.8) compared with 28.2 per 1000 people who did not receive surgery (95% CI 24.4 to 32.7).
  • People who already had diabetes at the time of their surgery were six times more likely to go into remission than controls (adjusted relative risk [RR] 5.97, 95% CI 4.2 to 7.8).
  • Health costs increased with body mass index, with obesity-related physical conditions and depression having the greatest influence on cost.
  • Each person undergoing surgery gained an additional 2.142 QALYs (95% CI 2.031 to 2.256). There was a high probability that surgery was cost-effective at usual NHS thresholds. For people with morbid obesity aged 20 to 74 years, the estimated cost per QALY gained was £7,129 (95% CI £6,775 to £7,506). In people with morbid obesity and diabetes, surgery was slightly more cost effective at £6,176 (95% CI £5,894 to £6,457).

What does current guidance say on this issue?

Weight loss surgery is recommended in NICE 2014 guidelines for people who are morbidly obese (BMI 40 or over). It is also recommended for people with severe obesity (BMI 35-39) and other health problems such as type 2 diabetes or high blood pressure. People of Asian ethnic origin with recent onset diabetes may be considered for surgery at a lower BMI.

What are the implications?

This study indicates that weight loss surgery is an effective way to reduce obesity and to reduce associated health problems which is cost-effective. The findings support current NICE recommendations, and the need to ensure that as many people as possible who meet eligibility criteria have access to surgery should it be indicated.

Commissioners will also need to consider the impact on total costs and how pathways for care could be adapted to make best use of the inevitable increasing use of weight loss surgery. This might include consideration of how the costs of providing earlier interventions for people in tier 1 to 3 services night reduce overall costs for weight loss surgery (see definitions).

In this study the additional costs associated with bariatric surgery were £15,258 and the costs of the procedures themselves were on average £9,164 per participant. If all those eligible took up an offer of surgery, this would have implications for health systems considering the long term affordability of these procedures.

People from black African, African-Caribbean and Asian (South Asian and Chinese) groups experience greater risk of associated complications at lower BMI than Caucasian people.

Additionally, obesity is associated with deprivation. Therefore, commissioners should consider health inequalities when assessing access to weight loss surgery.


Citation and Funding

Gulliford MC, Charlton J, Booth HP, et al. Costs and outcomes of increasing access to bariatric surgery for obesity: cohort study and cost-effectiveness analysis using electronic health records. Health Serv Deliv Res. 2016;4(17).

This project was funded by the National Institute for Health Research Health Services and Delivery Research programme. Martin C Gulliford and A Toby Prevost were supported by the NIHR Biomedical Research Centre at Guy’s and St Thomas’Hospitals. Peter Littlejohns was supported by the South London Collaboration for Leadership in Applied Health Research and Care. The funders did not engage in the design, conduct or reporting of the research.



NICE. Obesity: identification, assessment and management. CG189. London: National Institute for Health and Care Excellence; 2014.

PHE. UK and Ireland prevalence and trends. Public Health England; 2016.

PHE. Severe Obesity. Public Health England; 2016.

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Tiers of weight management services

Different tiers of weight management services cover different activities. Definitions vary locally but usually:

  • Tier 1 covers universal services (such as health promotion or primary care)
  • Tier 2 covers lifestyle interventions delivered in primary care
  • Tier 3 covers specialist and intensive weight management services
  • Tier 4 covers bariatric surgery


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