Treating cancer or leukemia in humans or animals, comprises placing the patient into artificial coma, and removing and/or treating tumors, abnormal cells and/or disease caused by an optimized protein-free or very low-protein extreme fasting cure, or placing the patient into artificial coma, and treating the disease using the body temperature by reducing and/or increasing continuously or in intervals as tumors and/or abnormal cells are very sensitive to external influences. The artificial coma is introduced e.g. after a cardiac arrest with successful resuscitation or after a major stroke. Treating cancer or leukemia in humans or animals, comprises placing the patient into artificial coma, and removing and/or treating tumors, abnormal cells and/or disease caused by an optimized protein-free or very low-protein extreme fasting cure, or placing the patient into artificial coma, and treating the disease using the body temperature by reducing and/or increasing continuously or in intervals as tumors and/or abnormal cells are very sensitive to external influences. The artificial coma is introduced e.g. after a cardiac arrest with successful resuscitation or after a major stroke, as the patient is cooled to 32-34[deg] C, and the cooling is very distressing and is bearable only in artificial coma. The extreme fasting cure, which is suitable for reducing tumors or abnormal cells or treating leukemia, is unacceptable over several weeks, and so is practicable by the artificial coma. The patient is placed into artificial coma for coma therapy, and natural foods or industrially produced liquid food are administered using a stomach tube, percutaneous endoscopic gastrostomy tube or intravenous feeding. A very small amount of food is administered over a long period of time in artificial coma. The healing effect compared to cancer is such that no excess tumor tissue is constructed due to the protein deficiency, but is degraded relatively fast as a fat storage. The fasting plays a crucial role and optionally promotes the immune system by the detoxifying effect or deprives living conditions of the cancer cells. The method optionally administers more food per unit of time or per day than normally or in intervals due to continuous food administration, optionally the blood values are checked regularly, and e.g. vegetable and/or fruit juices or a small amount of industrially produced protein-free or very low-protein liquid diet are administered for coma therapy, where the composition of the food is optimized compared to healing success. The coma treatment exactly determines food components e.g. egg whites or amino acids and proteins, fats, simple sugars or glucose and fructose, starch or cellulose, and optionally specific minerals or vitamins to be excluded, to reduce tumors or abnormal cells and/or to treat leukemia, and whether the receiving of little or plenty of water is beneficial e.g. using the tumor reduction and/or healing success is regularly controlled or based on twin studies. Additional vitamins and minerals e.g. calcium is administered for avoiding health damage. The blood values are regularly controlled during coma treatment to obtain optimal results, where the amount of food to be administered per unit of time is determined accurately. The optimal blood values are taken into experience e.g. based on twin studies, or is controlled regularly using the tumor reduction/healing success. Tables etc are prepared with the experienced data based on the food to be administered per unit of time, e.g. compared to body weight, body fat percentage, gender and age. The food is administered continuously, in intervals, or longer intervals during which no food is administered, is important for healing success, and the patients are to get used to after every few days to weeks of fasting back to a normal diet. The complete administering of food is excluded during coma therapy, but ensures no undesirable side effects e.g. muscle cramps. The duration of therapy coma is oriented on the healing success, or e.g. continues for forty days. A laxative is administered before the patient is placed into artificial coma or before the patient begins to fast. The treatment begins a few days before artificial coma with fasting, and the patient again slowly gets used to normal amount of nutrients, before the termination of the artificial coma. The coma is extended e.g. 2 days. The treatment is complemented by other forms of cancer or leukemia treatments.