PURPOSE OF REVIEW This study aims to assess various types of nutritional intervention for improving treatment tolerance in patients with malnutrition related to the cancer anorexia-cachexia syndrome. RECENT FINDINGS Malnutrition in cancer patients is associated with a poor prognosis, whereas weight loss is an important predictor of mortality. Disease and treatments have a major impact on nutritional status. By improving the latter, we can change the prognosis, quality of life and functional status, facilitating improved tolerance to treatment. Dietary counselling, recommended for patients at risk of malnutrition, should be introduced early in close collaboration with the patient. Administering oral nutritional supplements to malnourished patients has been shown to lead to a reduction in mortality, in complications and in the length of hospital stay. Supplementation with enteral nutrition has demonstrated an increase in appetite, energy intake, nutritional status and, above all, reduced gastrointestinal toxicity from cancer treatments due to a better response to them. Supplementation with home parenteral nutrition in aphagic and terminal patients has shown improved quality of life, energy balance, body composition and prolonged survival. SUMMARY Supplementation with ω3 fatty acids appears to offer benefits that are verifiable at a biochemical, clinical and functional level. Related literature, however, provides conflicting results; therefore further studies will be required to confirm their efficacy. Supplementation with glutamine appears to support the efficacy of chemoradiotherapy treatment while reducing toxicity of the tissues and improving outcomes. Oral supplementation with branched amino acid appears to reduce the length of hospital stay, decrease morbidity and improve the quality of life, without any changes in mortality. Perioperative supplementation with arginine has shown a reduced incidence of complications and a significant increase in long-term survival.