Malnutrition is highly prevalent in cancer patients as 15 to 40% of patients report weight loss at diagnosis. It is estimated that 40 to 80% of all cancer patients will be malnourished during the course of the disease. Furthermore, malnutrition can influence treatment outcomes, delay wound healing, worsen muscle function and increase the risk of post-operative complications. Metabolic and nutritional alterations consequent to malnutrition can influence survival and recovery of cancer patients leading to sarcopenia and cachexia. Sarcopenia is characterised by a decrease in lean body mass with an impact both on strength and physical function that may decrease the quality of life, and is often overlooked. Cancer cachexia is a complex multifactorial syndrome that results from a combination of metabolic alterations, systemic inflammation and decreased appetite.