You’ll start losing weight as soon as you’ve had gastric bypass surgery. Most people lose most of their excess weight in the first year. Weight loss can carry on after that, but will usually tail off in the second year as your weight settles.
See our section about gastric bypass surgery for more information.
Dumping syndrome is a possible side-effect of weight loss surgery. It can happen if you eat too much sugar. The stomach empties too quickly, which can cause sickness, dizziness and light-headedness.
There is more information in the section on gastric bypass surgery side-effects .
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- Obesity in adults. BMJ Best Practice. bestpractice.bmj.com, last updated June 2023
- Oxford Handbook of Endocrinology and Diabetes. Oxford Medicine Online. academic.oup.com, published November 2021
- Bariatric surgery sequelae. BMJ Best Practice. bestpractice.bmj.com, last reviewed May 2023
- Peterli R, Wolnerhanssen BK, Peters T, et al. Effect of laparoscopic sleeve gastrectomy vs laparoscopic Roux-en-Y gastric bypass on weight loss in patients with morbid obesity: The SM-BOSS
- Randomized Clinical Trial. JAMA 2018; 319(3):255–65. doi: 10.1001/jama.2017.20897
- Gronroos S, Helmio M, Juuti A, et al. Effect of laparoscopic sleeve gastrectomy vs Roux-en-Y gastric bypass on weight loss and quality of life at 7 years in patients with morbid obesity: The SLEEVEPASS Randomized Clinical Trial. JAMA Surg 2021; 156(2):137–46. doi: 10.1001/jamasurg.2020.5666
- Roux-en-Y Gastric Bypass and Sleeve Gastrectomy. University Hospitals Plymouth NHS Trust. plymouthhospitals.nhs.uk, published May 2023
- Laparoscopic gastric bypass. Medscape. emedicine.medscape.com, last updated April 2023
- Life after weight-loss surgery. Medline Plus. medlineplus.gov, last reviewed July 2021
- Obesity: identification, assessment and management. National Institute for Health and Care Excellence. nice.org.uk, last updated September 2022
- Eisenberg D, Shikora SA, Aarts E, et al. 2022 American Society of Metabolic and Bariatric Surgery (ASMBS) and International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO) Indications for Metabolic and Bariatric Surgery. Obesity Surgery 2023; 33(1):3, published November 2022
- Bariatric Surgery. MSD Manuals. msdmanuals.com, last reviewed August 2021
- Anaesthesia explained. Royal College of Anaesthetists. rcoa.ac.uk, published March 2021
- O'Kane M, Parretti H, Pinkney J, et al. British obesity and metabolic surgery society guidelines on perioperative and postoperative biochemical monitoring and micronutrient replacement for patients undergoing bariatric surgery—2020 update. Obes Rev 2020; 21(11). doi: org/10.1111/obr.13087
- Romeijn M, Kolen AM, Holthuijsen DDB, et al. Effectiveness of a low-calorie diet for liver volume reduction prior to bariatric surgery: a systematic review. Obes Surg 2021; 31(1):350–56
- Laparoscopic gastric bypass periprocedural care. Medscape. emedicine.medscape.com, last updated April 2023
- Anaesthesia Explained: On the day of your operation. Royal College of Anaesthetists. rcoa.ac.uk, published March 2021
- Venous thromboembolism in over 16s: reducing the risk of hospital-acquired deep vein thrombosis or pulmonary embolism. National Institute for Health and Care Excellence. nice.org.uk, last updated August 2019
- Decision making and consent. General Medical Council. gmc-uk.org, published November 2020
- Personal communication, Mr Peter Lamb, Consultant General and Upper Gastrointestinal Surgeon, July 2023
- Bariatric Surgery. Patient. patient.info, last updated April 2023
- Types of weight-loss surgery. National Institute of Diabetes and Digestive and Kidney Diseases. niddk.nih.gov, last updated September 2020
- Oxford Handbook of Operative Surgery (3rd ed). Oxford Medicine Online. academic.oup.com, published May 2017
- Thorell A, MacCormick AD, Awad S, et al. Guidelines for perioperative care in bariatric surgery: enhanced recovery after surgery (ERAS) society recommendations. World J of Surg 2016; 40:2065–83
- Roux en Y gastric bypass (RYGB). Royal Berkshire NHS Foundation Trust. royalberkshire.nhs.uk, published August 2020
- Oxford Handbook of Adult Nursing (2nd ed). Oxford Medicine Online. academic.oup.com, published June 2018
- Life After Bariatric Surgery. American Society for Metabolic and Bariatric Surgery. asmbs.org, last updated February 2021
- Aguas-Ayesa M, Yarnoz-Esquiroz P, Olazaran L, et al. Precision nutrition in the context of bariatric surgery. Rev Endocr Metab Disord 2023; Mar 17:1–13. doi: 10.1007/s11154-023-09794-5
- Alyahya RA, Alnujaidi MA. Prevalence and outcomes of depression after bariatric surgery: A systematic review and meta-analysis. Cureus 2022;14(6): e25651. doi. 10.7759/cureus.25651
- Going home after a laparoscopy (adult). Milton Keynes University Hospital NHS Foundation Trust. mkuh.nhs.uk, accessed June 2023
- Dumping syndrome clinical presentation. Medscape. emedicine.medscape.com, last updated June 2019
- Dumping syndrome. Medscape. emedicine.medscape.com, last updated June 2019
- Eating, Diet, & Nutrition for Dumping Syndrome. National Institute of Diabetes and Digestive and Kidney Diseases. niddk.nih.gov, last reviewed January 2019
- Common postoperative complications. Patient. patient.info, last updated November 2020
- Tips on a speedier recovery after surgery. University Hospital Southampton NHS Foundation Trust. uhs.nhs.uk, last reviewed March 2020
- Bariatric surgery. Medscape. emedicine.medscape.com, last updated March 2023
- Weight-loss Surgery Benefits. National Institute of Diabetes and Digestive and Kidney Diseases. niddk.nih.gov, last updated September 2020
- Bariatric surgery treatment and management. Medscape. emedicine.medscape.com, last updated March 2023
- Swallowable gastric balloon capsule for weight loss. National Institute for Health and Care Excellence. nice.org.uk, last updated November 2020