Nutrition and lifestyle have the principal role in etiology of diabetes mellitus type 2. T2DM is a disease that is caused by chronical energy excess that damaged the basic regulation systems. T2DM is not caused by a (relative or absolute) lack of insulin and it is not caused by inborn insulin resistance. The insulin “pseudo-resistance” is present; it is a sign of active intracellular defence. It is therefore temporarily influenceable. T2DM is caused by a collision of basic hormonal systems (insulin, glucagon, GLP1, adiponectin, cortisol, ACTH, epinephrine, amylin and other hormones), and intracellular regulatory system (AMPK and other “intracellular hormones”). The optimal therapy of the early stage of T2DM is probably not insulin administration, but drugs which have an anorectic effect (incretin mimetics, glukagon like peptide-1 analogs), drugs, which diminish the effectivity of metabolism (metformin), bariatric surgery, endobarrier or drugs, that directly remove the glucose (gliflozins). Adequate food intake and physical training have no dangerous side effect.