Bariatric Surgery
Surgical procedures that alter the digestive system to promote weight loss.
Plain English
Patient-Friendly Explanation
Bariatric surgery changes the stomach and sometimes the intestinal tract so that you eat less and absorb fewer calories. The main operations are the sleeve gastrectomy (the stomach is reduced to a narrow tube) and the gastric bypass (the stomach is made small and connected further down the intestine). It produces the largest average weight loss of any treatment — often 20 to 30 per cent of body weight — and can improve or put type 2 diabetes into remission. It is also permanent, carries surgical risks including bleeding, infection, clots and nutritional deficiencies for life, and requires permanent dietary changes and vitamin supplementation. In Singapore it is generally considered for people with a BMI of 37.5 or above, or 32.5 or above with a weight-related condition such as diabetes, after other approaches have been tried. It requires assessment by a surgical team, and lifelong follow-up.
Medical
Clinical Definition
Bariatric surgery comprises restrictive and malabsorptive procedures. Sleeve gastrectomy (SG) reduces gastric volume via greater-curvature resection and lowers ghrelin; Roux-en-Y gastric bypass (RYGB) combines a small gastric pouch with intestinal bypass, altering nutrient absorption and gut-hormone secretion. In the landmark STAMPEDE and Swedish Obese Subjects studies, surgery produced durable weight loss and improved glycaemic control versus medical therapy; average excess-weight loss is roughly 50-70% at 2-5 years, with substantial variability and some regain over a decade. Perioperative risks include anastomotic leak, bleeding, venous thromboembolism, and mortality around 0.1-0.5% in experienced centres. Long-term risks include micronutrient deficiencies (iron, B12, folate, calcium, vitamin D) requiring lifelong supplementation, dumping syndrome, and gallstone formation. Candidacy in most guidelines: BMI >= 40 (or >= 35 with comorbidity) by international criteria, adjusted in Asia to >= 37.5 and >= 32.5 with comorbidity. Bariatric surgery is not a substitute for lifestyle change and requires multidisciplinary assessment and lifelong follow-up; in an era of effective pharmacotherapy, it is positioned for patients who need the largest intervention or who have failed medical treatment.
Key Insight
Why It Matters
Bariatric surgery sits at the top of the weight-treatment ladder: the largest results, the largest commitment. It suits people whose health is at serious risk and for whom less invasive treatment has not worked. The honest comparison in 2026 is with the modern GLP-1 medicines, which produce smaller average losses but are reversible, non-surgical and far lower risk. That does not make surgery obsolete (it remains the most effective option for patients in the highest BMI ranges, and it improves diabetes powerfully), but it changes the order of the conversation: for most people, medical treatment with structured support is tried first, and surgery is discussed when that is insufficient. Either way, the decision is made by a team, not by a single consultation.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: August 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
