Abstract: Changing the normal metabolic environment of cancer cells by using artificial diets in which the levels and ratios of specific amino acids and lipids are manipulated. Because of their DNA alterations, cancer cells will not be able to fully adapt to the new metabolic environment, which will reduce their survival capacity and their protection against the immune system. Artificial diet compositions are provided that induce remarkable anticancer activities in animal models of metastatic cancers; these activities were higher than in mice receiving the pharmacological treatments used in cancer patients. The levels of methionine and leucine have a major impact on the in vivo anticancer activity of the diets. In all the active diets, the levels of methionine are less than or equal to 0.6% and the levels of leucine are less than or equal to 10%, based on the total weight of the whole dry composition.