Bariatric surgery is associated with long-term weight loss and health risk reductions

December 22, 2015

Bariatric surgery delivered in routine clinical practice in the UK is associated with a substantial initial weight loss that is sustained for at least four years after surgery, according to a study published this week in PLOS Medicine. The longitudinal study, conducted by Ian Douglas and colleagues at the London School of Hygiene & Tropical Medicine, UK, also shows that bariatric surgery is associated with improvements in pre-existing type 2 diabetes and hypertension and with a reduced risk of the onset of several obesity-related co-morbidities.

Bariatric surgery has helped obese people lose weight in randomized controlled trials, but the benefits for patients' broader health over a longer period have not been as well studied. Here, the researchers investigated whether there was an association between bariatric surgery and subsequent weight, BMI, and obesity-related illnesses in a study of 3882 bariatric surgery patients and similar control patients who did not have surgery, tracked using primary care records in the UK Clinical Practice Research Datalink. Bariatric surgery patients lost weight at a rate of 4.98 kg/month (95% Confidence Intervals 4.88 to 5.08) during the first four post-operative months (versus no change in the comparision group); their weight loss was sustained at a slower rate for four years. Bariatric surgery was also associated with a reduced risk of getting a new diagnosis of type 2 diabetes (Hazard Ratio with 95% CI: 0.68 (0.55-0.83)), hypertension (0.35 (0.27-0.45)), angina (0.59 (0.40-0.87)), heart attack (0.28 (0.10-0.74)), and obstructive sleep apnea (0.55 (0.40-0.87)). Surgery was also associated with increased resolution of both type 2 diabetes (9.29 (6.84 - 12.62)) and hypertension (5.64 (2.65-11.99) among people who already had these conditions. The investigators did not detect an association between bariatric surgery and reduced mortality in this study, but noted that longer follow-up may be needed to establish associations with mortality.

The accuracy of these findings may be limited by the incomplete recording of some outcomes in primary care patient management records. Nevertheless, these results suggest that widening the availability of bariatric surgery in the UK could provide substantial health benefits for people who are very obese. The authors estimate that, assuming these associations are causal, broader use of bariatric surgery in the UK over four years could prevent or resolve roughly 93,000 cases of hypertension and 149,000 cases of type 2 diabetes.
Research Article


IJD is funded by a Medical Research Council Fellowship (G0802403/1). LS is funded by a Wellcome Trust Fellowship. RLB is funded by the Rosetrees Trust. KB holds a Sir Henry Dale Fellowship jointly funded by the Wellcome Trust and the Royal Society (grant number 107731/Z/15/Z). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests:

I have read the journal's policy and the authors of this manuscript have the following competing interests: RLB has consulted for GlaxoSmithKline and received honoraria from Ethicon and Pfizer.


Douglas IJ, Bhaskaran K, Batterham RL, Smeeth L (2015) Bariatric Surgery in the United Kingdom: A Cohort Study of Weight Loss and Clinical Outcomes in Routine Clinical Care. PLoS Med 12(12): e1001925. doi:10.1371/journal.pmed.1001925

Author Affiliations:

Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, United Kingdom

Centre for Obesity Research, Rayne Institute, Department of Medicine, University College London, London, United Kingdom

University College London Hospitals Bariatric Centre for Weight Management and Metabolic Surgery, London, United Kingdom

National Institute of Health Research, University College London Hospitals Biomedical Research Centre, London, United Kingdom



Ian Douglas
London School of Hygiene & Tropical Medicine
Department of Epidemiology & Population Health

Press Office
London School of Hygiene & Tropical Medicine
Department of Epidemiology & Population Health
Keppel Street
London, WC1E 7HT


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