Being overweight alone does not automatically make someone a candidate for bariatric surgery. Eligibility depends on factors such as BMI, obesity-related health conditions, previous weight-management efforts and overall health. A comprehensive assessment also considers eating patterns, medical history, medicines and the patient's readiness to make permanent changes to diet, physical activity and follow-up care. The decision is individualized and is often made by a multidisciplinary team that may include surgeons, physicians, dietitians and behavioral health professionals.

Common bariatric procedures include sleeve gastrectomy and Roux-en-Y gastric bypass. Other procedures, such as biliopancreatic diversion with duodenal switch and single-anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S), may be considered in selected patients. These procedures work in different ways: some primarily reduce the amount of food the stomach can hold, while others also alter nutrient absorption or affect hormones involved in hunger and fullness. The most appropriate procedure depends on the patient's health, BMI, eating patterns and treatment goals.

Bariatric surgery changes the digestive system in ways that can reduce food intake, alter nutrient absorption and, with some procedures, influence hormones involved in appetite and fullness. The resulting weight loss can improve several obesity-related conditions, including type 2 diabetes, high blood pressure, sleep apnea, abnormal cholesterol levels and metabolic dysfunction-associated steatotic liver disease. It may also improve mobility and overall quality of life. Long-term results depend not only on the procedure but also on sustained changes in eating habits and physical activity.

Before surgery, patients typically undergo a comprehensive assessment to determine whether surgery is appropriate and to identify factors that could affect treatment or recovery. This may include reviewing weight history, eating and activity patterns, medical conditions and medicines, along with a physical examination and laboratory testing. Additional assessments may evaluate conditions such as diabetes, high blood pressure, liver problems or other obesity-related health concerns. Patients may also receive nutritional and behavioral evaluation and specific instructions about medicines, eating, physical activity and smoking before surgery.

Bariatric surgery requires lifelong changes rather than being a standalone solution for weight loss. Immediately after surgery, patients generally progress from liquids to pureed or soft foods and eventually to regular foods in carefully controlled portions. Long-term care focuses on balanced nutrition, appropriate portion sizes, regular physical activity and taking prescribed vitamin or mineral supplements when required. Regular follow-up and blood tests may be needed to monitor nutrition and overall health. Maintaining these changes is essential for achieving and sustaining the benefits of surgery.

Bariatric surgery can produce substantial, long-term weight loss and may improve or even resolve several obesity-related health conditions, including type 2 diabetes, hypertension and sleep apnea. However, it is a major surgical procedure and carries potential risks. Short-term complications can include bleeding, infection, blood clots, anaesthesia-related problems and leaks. Longer-term complications vary by procedure and may include nutritional deficiencies, gallstones, bowel obstruction, reflux or the need for additional surgery. Regular long-term follow-up is therefore an important part of care.