The diagnosis of cachexia is based on loss of body weight and low body mass index plus at least three out of five additional criteria: decrease in muscle strength, fatigue, anorexia, low lean body mass, and abnormal biochemistry. Cachexia affects 50-80% of cancer patients, accounting for up to 20% of all cancer-related deaths. Cachexia is associated with increased incidence of doselimiting chemotherapy toxicity and higher odds of treatment discontinuation. Energy wasting resulting from an imbalance between energy requirements and energy uptake is proposed to contribute to cachexia. Muscle protein breakdown, acceleration of myonuclear apoptosis, and impaired muscle regeneration contribute to nitrogen imbalance and muscle wasting in cachexia. Identifying personalised nutritional needs and developing tailored nutritional plans are pillars of cachexia treatment. Substances with muscle anabolic activities may represent a pharmacological option to contrast cachexia. Multimodal treatment protocols should involve a multidisciplinary team of health professionals as well as patients and their formal and informal caregivers.