Malnutrition or "undernutrition" in adults (≥18 years of age) is the deficiency of nutrients (energy, protein and micronutrients) which causes adverse effects on bodily composition, clinical and functional outcomes. Malnutrition can occur as a result of a number of factors including inadequate calorie intake, impaired nutrient absorption (malabsorption/maldigestion) or increased energy requirements usually associated with disease/illness e.g. cancer, inflammatory bowel disease and pancreatitis, and its management, e.g. chemotherapy and surgery. Patients who have or are at risk of malnutrition can be managed with a range of nutrition support strategies, including the use of oral nutritional supplements and enteral feeds (administered by feeding tubes such as nasogastric tubes, gastrostomies or jejunostomies). These feeds may provide either a sole source of nutrition or in combination with the diet.