Summary: Oncological diseases markedly changes metabolic pathways, which are less effective in comparison with physiological ones. In other words, the outcome of the modified metabolism is a lower gain of high-energy substrates, e.g. ATP. This energy deficit is to be substituted. Concurrently with the substitution of so needed substrates we encounter a series of unfavorable factors, which not only decrease and change appetite, but they also increase aversion against some kinds of food, and deteriorate chewing and swallowing of food. The therapy of oncological diseases itself increases the above mentioned negative factors even more.

        Key words: malnutrition - weight loss - complication in nutrition