The decrease in the expression of ghrelin, irisin, and titin on the level of mRNA and proteins, which we have noted, as well as determination of the status of methylation of those genes in combination with available data from the literature show that the observed expression profile of ghrelin, irisin, and titin is above all a result of cancer cachexia and malnutrition. The gene discussed is FNDC5; the disease is malnutrition.