Bariatric surgery is considered the most effective treatment for morbid obesity. The intervention involves modification of the gastrointestinal anatomy and motility and, in combination with other factors, contributes to prolonged weight loss. This narrative literature review summarises the current evidence for the role of nutrition before and after bariatric surgery. It covers preparation for surgery and how nutrition can reduce complications, alongside the importance of nutrition in the post-operative phase, where it can be vital to the success of the intervention. As bariatric surgery alters digestive functions, macro-and micronutrient malabsorption and deficiencies are common in such candidates. Issues around protein malabsorption and altered carbohydrate and fibre digestion are discussed, in addition to vitamins and minerals. To negate the inherent risks of deficiencies, the authors advocate for life-long supplementation and routine testing for vitamin and mineral status. Gastrointestinal symptoms are equally common after bariatric surgery, and nutritional management being suggested as an effective intervention in many cases. Symptoms covered include dumping syndrome, diarrhoea, flatulence, small intestinal bacteria overgrowth (SIBO), steatorrhea, dysphagia, vomiting and food intolerances. The review also briefly summarises current knowledge of bariatric surgery and its nutritional impact concerning preconception, conception, pregnancy and lactation. Beyond nutritional care, the writers acknowledge the pertinence of additional counselling on eating behaviours, lifestyle choices and the importance of engagement and adherence as key to the success of bariatric surgery and long-term weight loss. The nutritional considerations in this review provide useful guidance for the support of individuals preparing or recovering from bariatric surgery.