Among many oncological patients we can notice a substantial loss of body weight, fat and proteins with significant proinflammatory activity at the time of diagnosis. This wasting condition is well known as cancer cachexia syndrome. Anorexia is important part of this syndrome. Because cancer cachexia reduces tumor response to treatment and it is an indicator of poor prognosis, we need to start correcting these nutritional deficits at once. In the presence of cancer cachexia it is extremely difficult to achieve protein anabolism and stop the body wasting by standard nutritional formulas only. During the last few years, the use of eicosapentaenoic acid (EPA) and megestrol acetate (MA) as anticahectic agents has been tested. These guidelines are intended to give evidence-based recommendations for the use of eicosapentaenoic acid and megestrol acetate in cancer cachexia syndrome. These guidelines have been developed by interdisciplinary expert group of Croatian clinicians. Based on relevant literature, we have concluded that the use of metabolic modulators such as eicosapentaenoic acid and megestrol acetate for 8 weeks may help to improve nutritional status in cachectic patients.