Malnutrition is common in cancer patients and is usually underdiagnosed. There is a need to identify it in order to prevent anorexia and cachexia.To understand and prevent anorexia and cachexia we need to understanding the gut-brain dysfunction and mechanisms that affect food intake. Many mediators and cytokines are involved in the feeling of hunger and satiety including ghrelin and leptin.Discussed are the mechanisms of action of those mediators and their influence on hunger and anorexia development. Many factors are involved in hunger signaling, the main pathways involved in ghrelin and that pathway is altered during cancer anorexia where ghrelin resistance develops. There is also evidence that there is a loss of adaptation to energy depletion in cancer patients. Normally when losing weight the circulating leptin decreases causing food intake to increase, however in cancer patients this does not trigger an increase in food consumption. It has been hypothesized that anorexia in cancer patients is likely due to ghrelin resistance and enhanced satiation, however many factors and mediators are involved in the process. Furthermore, chemotherapy is associated with dyspepsia, vomiting, fatigue and anorexia and chemotherapy treatment with cis-platin interferes with ghrelin and its action on the hypothalamic receptors. Another possible cause for anorexia during chemotherapy treatment is chemosensory abnormalities. Although very little data is available a study has shown that during cancer the gut microbiota was altered which had an impact on hunger and satiety.Chronic diseases can cause depression, anxiety and altered appetite which can then cause possible brain-gut dysfunction and vis versa. The conclusion of this presentation is that there is a need to integrate our understanding of cancer anorexia, the gut microbiota-brain axis, the role of intestinal taste/gust cells and an integrated psychological approach but the most important would be to detect the onset of anorexia at an early stage.