Background: One of the fundamental metabolic characteristics of cancer tissues is high consumption of glucose by cancer cells. The purpose of this article is determination of the features in the energy metabolism of cancer cells, elucidation of energy metabolism due to the major nutritive substrates, such as glucose and glutamine, evaluation of lactate dehydrogenase (LDH) as a potential marker of malignancies, estimation of the ketogenic diet in the treatment of cancer. The cells with higher degree of proliferation have a lower level of reduced Nicotinamide Adenine Dinucleotide (NADH), confirming the hypothesis: anabolic processes are predominant in cancer. The preferred way of glucose utilization in cancer tissues is the conversion of pyruvate to lactate, a phenomenon known as aerobic glycolysis or Warburg effect. Tumors with a high level of aerobic glycolysis are the most aggressive. The fact that LDHA (which catalyzes the reversible reaction of pyruvate to lactate) reflects the aggressiveness of the tumor and demonstrates the importance of aerobic glycolytic metabolism (the Warburg effect) in the survival of tumor cells. Conclusions: Multiple studies have mentioned the possibility of using glutamine instead of glucose by the cancer cells. Use of glutamine is another way of generating energy contributing to tumor cell survival. It was established that on substitution of glucose with ketone bodies (ketogenic diet), cancer cells can not adapt and die. Modulation of energy metabolism represents a new stage in the treatment of cancer. The substitution of glucose with lipids in the feed ration (ketogenic diet) is a non-toxic method of cancer management, both in prevention and treatment .