There appears to be a misconception being perpetrated that the body does not normally burn fat. On the contrary most tissues can and do use fatty acids as their primary if not sole, source of metabolic energy. Under normal circumstances the exception to this is the brain and nervous tissues as well as red blood cells. Before discussing ketosis we must first define ketones.
Ketones are intermediate products in the oxidation of fat to energy.
There are three types of ketones - acetoacetate, Beta hyroxybutyrate and acetone. They are synthesized in the liver. Once formed they enter the blood stream and are further metabolized outside the liver by skeletal muscles, heart, brain, kidney and intestine. Complete break down of ketone bodies to energy requires certain chemicals derived from another cycle of chemical reactions called the Tricarboxolic acid cycle. As the level rises our body tries to dispose of the excess ketones.