Cancer, more commonly called a tumor, is an abnormal and abnormal growth of cells that can originate from an organ or a tissue. The neoplastic patient frequently presents, from the onset of the disease, a weight loss with a variable incidence depending on the location, type and stage of the disease. Patients at greatest risk of energy-caloric malnutrition are those affected by tumors affecting the gastrointestinal tract (stomach, pancreas, colorectal) and the head and neck area. With the evolution of the disease, there is a progressive deterioration of the nutritional status due to the direct effect of the growth of the tumor to the detriment of the body’s tissues, due to the metabolic mechanisms that are triggered by the tumor / host interaction or as a consequence of oncological treatments .