The regulation of food intake is mediated by different psicological, gastrointestinal metabolic, nutritional and endocrine mechanisms. The cancer patient suffers from anorexia which results in early saciety and a reduction of appetite. Sometimes, the causes of the anorectic response are derived from the antitumoral treatment (chemotherapy, radiotherapy or immunotherapy), in some cases vomiting resulting in altered food intake. Alterations in the food taste and smell perception in addition to psychological dearrangements might also lead to the anorexia. Sometimes the tumour may play a direct effect when it is localised in either the hypothalamus or the digestive apparatus. However, in the majority of cases the origin of the anorexia associated with cancer cachexia seems to be due to the metabolic alterations induced by tumour burden. Different factors of both humoral and tumoral origin play a role in cancer anorexia. For instance, tumour necrosis factor (TNF-), a cytokine responsible for a great part of the metabolic alterations characteristic of cancer cachexia seems to be involved. In conclusion, the cancer anorexia seems to be more an effect than the cause of the weight loss and in fact the decrease in food intake might take place after weight loss is evident. In any case, the malnutrition associated with a decrease of food intake worsens the cachectic state, favouring a kind of a positive feed-back mechanism that finally leads to the patient's death.