Definition for Ketosis
From Biology Forums Dictionary
1) Ketosis is a state of elevated levels of ketone bodies in the body. It is almost always generalized throughout the body, with hyperketonemia, that is, an elevated level of ketone bodies in the blood. Ketone bodies are formed by ketogenesis when liver glycogen stores are depleted. The ketone bodies acetoacetate and β-hydroxybutyrate are used for energy.
2) In general, if you do not eat enough carbohydrate to support regular exercise, your body will have to rely upon fat and protein as alternative energy sources. While most of the body tissues can use fat and protein for energy, the brain prefers to use glucose. Thus, when carbohydrate intake is too low, the body begins to break down stored fat to produce an alternative fuel called ketones.