In the starvation the level of glucose in blood plasma is decreased. It causes the stimulation of glycogenolysis and inhibition of biosynthesis of proteins. The storage of glycogen is finished in 12-24 hours of starvation and lipolysis and gluconeogenesis start. Thus, in 1-st week of starvation the lipolysis and gluconeogenesis dominate. The brain in this period can use the glucose and glucogenic aminoacids as energetic sources.
The 2-nd period of starvation beginns from 2-nd week. In this period the gluconeogenesis is decreased and the ketogenesis is increased. The brain beginns to use the ketone bodies as energetic source. Beside of ketogenesis the part of acetylCoA is used for synthesis of cholesterol therefore the hypercholesterolemia is observed.
The 3-rd period of starvation (terminal or period of decompensation) conform to loss of 40-50% of body weight with loss of 100% of reserve fat and almost of 97% fat of organs. This period is characterized by increase of cleavage of proteins and development of hypernitrogenemia.