Introduction to the BOMSS GP Hub

16 March 2023

Bariatric surgery: the long-term health benefits and potential complications

Bariatric surgery is the most clinical – and cost-effective treatment for severe obesity[1-4]. In England, on average, 6500-7000 procedures are performed annually and around 75,000 patients had bariatric surgery between 2008-2019[5-6]. Bariatric surgery works by influencing complex biological processes including influencing the gut hormones that control appetite and satiety, reducing the absorption of nutrients, and mechanical effects. Information about the different bariatric surgery procedures can be found here.

Bariatric surgery has multiple health benefits, for example improvements in type 2 diabetes mellitus, hypertension and obstructive sleep apnoea, and reductions in overall mortality[4,6-9]. Despite these significant benefits, in the long-term bariatric surgery can result in multiple issues including nutritional deficiencies[10-13]. Micronutrient deficiencies can be common after bariatric surgery, for example the reported prevalence of iron deficiency is 30%, vitamin B12 19-35%, folic acid 9-39% and vitamin D 25-73%[14]. Several studies have suggested that those who do not have regular follow-up are more likely to have poorer outcomes, including developing nutritional deficiencies[15-19]. In addition to nutritional issues, patients may experience psychological issues post-bariatric surgery, and some may experience complications from surgery such as internal hernias, ulcers or post-prandial hypoglycaemia[20-26]. Patients who have bariatric surgery tend to have obesity related co-morbidities pre-surgery, which will need to continue to be monitored following surgery (initially this may need to be more frequent during rapid weight loss post-surgery)[27].

Lifelong nutritional care after bariatric surgery

The National Institute for Heath and Care Excellence (NICE) have recognised the importance of follow-up for these patients and NICE CG189 recommended patients have specialist follow-up with their bariatric surgery team for the first 2 years post-surgery and are then discharged to GPs to continue to have lifelong annual reviews (including nutritional monitoring) under a shared-care model. Other organisations such as the European Association for the Study of Obesity and the National Confidential Enquiry into Patient Outcome and Death have also highlighted the importance of long-term follow-up for patients after bariatric surgery.

Guidance for nutritional monitoring and supplementation: annual nutritional reviews in primary care

In the UK, the British Obesity and Metabolic Surgery Society (BOMSS) have published detailed guidelines for nutritional monitoring and management of patients who have had bariatric surgery. However, given the length of the document, it is not easily accessible for GPs. Therefore, a working group comprising GPs, bariatric dietitians and a chemical pathologist, with expertise in obesity and bariatric surgery, was formed to develop a more accessible summary of BOMSS nutritional guidance to support GPs with the lifelong management of patients after bariatric surgery, which can be found here.

It is important to note that a full annual review includes medical, nutritional and psychological components. On this webpage you will also find links to more detailed guidance for GPs for post-bariatric surgery annual reviews, including a pre-consultation questionnaire for patients and a GP consultation guide.

A full post-bariatric review may appear burdensome, but it should be noted that much of a post-bariatric annual review overlaps with other long-term condition reviews and/or a medication review routinely conducted in primary care. It also provides an opportunity to identify any difficulties as early as possible and may prevent significant care needs in the future.

The challenges: commissioning for shared-care after bariatric surgery

There is still a lack of commissioned shared-care services to provide long-term post-bariatric surgery follow-up, both in primary and secondary care. There is an urgent need to develop this, including considering new virtual consultations; for those involved in commissioning, some potential shared-care models can be found at here.


1. National Institute for Health and Care Excellence. Obesity: identification, assessment and management. Clinical guidance [CG189] 2014 Available from:
2. Picot J et al. The clinical effectiveness and cost-effectiveness of bariatric (weight loss) surgery for obesity: A systematic review and economic evaluation. Health Technology Assessment. 2009;13(41):ix-214.
3. Puzziferri N et al. Long-term follow-up after bariatric surgery: a systematic review. JAMA. 2014;312(9):934-42.
4. Sjostrom L. Review of the key results from the Swedish Obese Subjects (SOS) trial – a prospective controlled intervention study of bariatric surgery. Journal of Internal Medicine. 2013;273(3):219-34.
5. NHS Digital. Statistics on Obesity, Physical Activity and Diet, England, 2020 2020 Available from:
6. British Obesity and Metabolic Surgery Society. Third National Bariatric Surgery Registry Report preview 2017 Available from:
7. Debédat J et al. Long-term Relapse of Type 2 Diabetes After Roux-en-Y Gastric Bypass: Prediction and Clinical Relevance. Diabetes Care. 2018;41(10):2086-95.
8. Tsilingiris D et al. Remission of Type 2 Diabetes Mellitus after Bariatric Surgery: Fact or Fiction? Int J Environ Res Public Health. 2019;16(17):3171.
9. Buchwald H et al. Bariatric Surgery: A Systematic Review and Meta-analysis. JAMA. 2004;292(14):1724-37.
10. Puzziferri N et al. Long-term follow-up after bariatric surgery: a systematic review. JAMA. 2014;312(9):934-42.
11. Mechanick JI et al. Clinical Practice Guidelines For The Perioperative Nutritional, Metabolic, And Nonsurgical Support Of The Bariatric Surgery Patient-2013 Update: Cosponsored By American Association Of Clinical Endocrinologists, The Obesity Society, And American Society For Metabolic & Bariatric Surgery. Endocrine Practice. 2013;19(2):337-72.
12. Aills L et al. ASMBS Allied Health Nutritional Guidelines for the Surgical Weight Loss Patient. Surg Obes Relat Dis. 2008;4(5 Suppl):S73-108.
13. Parrott J et al. American Society for Metabolic and Bariatric Surgery Integrated Health Nutritional Guidelines for the Surgical Weight Loss Patient 2016 Update: Micronutrients. Surgery for Obesity and Related Diseases. 2017;13(5):727-41.
14. Lupoli R et al. Bariatric surgery and long-term nutritional issues. World J Diabetes. 2017 15;8(11):464-474.
15. Schijns W et al. Do specialized bariatric multivitamins lower deficiencies after RYGB? Surg Obes Relat Dis. 2018;14(7):1005-12.
16. Kim HJ et al. Does patient compliance with follow-up influence weight loss after gastric bypass surgery? A systematic review and meta-analysis. Obes Surg. 2014;24(4):647-51.
17. Athanasiadis DI et al. Factors associated with weight regain post-bariatric surgery: a systematic review. Surg Endosc 2021:35, 4069–4084.
18. Karefylakis C et al. Prevalence of anemia and related deficiencies 10 years after gastric bypass–a retrospective study. Obes Surg. 2015;25(6):1019-23.
19. Harbottle L. Audit of nutritional and dietary outcomes of bariatric surgery patients. Obesity Reviews. 2011;12(3):198-204.
20. Wilson HO et al. Complications from micronutrient deficiency following bariatric surgery. Annals of Clinical Biochemistry. 2014;51(6):705-9.
21. Ma IT et al. Gastrointestinal Complications After Bariatric Surgery. Gastroenterol Hepatol. 2015;11(8):526-35.
22. Eisenberg, Dan et al. ASMBS Position Statement on Postprandial Hyperinsulinemic Hypoglycemia after Bariatric Surgery. Surgery for Obesity and Related Diseases, 2017; 13(3): 371 – 378.
23. Mitchell JE et al. Possible risk factors for increased suicide following bariatric surgery. Obesity 2013;21(4):665-72.
24. King WC et al. Prevalence of Alcohol Use Disorders Before and After Bariatric Surgery. JAMA. 2012;307(23):2516-25.
25. Parretti HM et al. ‘The rollercoaster of follow-up care’ after bariatric surgery: a rapid review and qualitative synthesis. Obes Rev. 2019;20(1):88-107.
26. Mitchell JE et al. Course of depressive symptoms and treatment in the longitudinal assessment of bariatric surgery (LABS-2) study. Obesity 2014;22:1799–806.
27. Busetto L et al. Practical Recommendations of the Obesity Management Task Force of the European Association for the Study of Obesity for the Post-Bariatric Surgery Medical Management. Obesity Facts. 2017;10(6):597-632.

© BOMSS and the authors 2023