Bariatric surgery has many benefits beyond weight loss, including improved control of glycaemia, blood pressure, and dyslipidaemia; hence, such surgery has been rebranded as metabolic surgery. The operations are, unfortunately, also associated with major surgical and medical complications. The medical complications include gastro-oesophageal reflux disease, malnutrition, and metabolic complications deriving from vitamin and mineral malabsorption. The benefits of surgery can be optimised by implementing specific protocols before and after surgery. In this Review, we discuss the assessment of the risk of major cardiac complications and severe obstructive sleep apnoea before surgery, and the provision of adequate lifelong postsurgery nutritional, vitamin, and mineral supplementation to reduce complications. Additionally, we examine the best antidiabetic medications to reduce the risk of hypoglycaemia after gastric bypass and sleeve gastrectomy, and the strategies to improve weight loss or reduce weight regain. Although optimising clinical pathways is possible to maximise metabolic benefits and reduce the risks of complications and micronutrient deficiencies, evolution of these strategies can further improve the risk-to-benefit ratio of metabolic surgery.