A ketogenic diet is a diet in which most of the calories come from fat (70-75%). A moderate amount of calories come from protein (20-25%). Only a small number of the calories come from carbohydrates (5%).
The diet forces the body to burn fats rather than carbohydrates for energy. Normally, the carbohydrates you eat are turned into glucose in the body, which is used for energy around the body and in the brain. But, if you don't eat enough carbohydrates, your body has a back-up system of burning fat instead. The liver can use stored fat and the fat you eat for energy. Stored fat is broken into two parts, fatty acids, and ketone bodies. Ketone bodies power the brain instead of glucose. This state of having a lot of ketone bodies in your blood is called "Ketosis." The liver can also make or release its own glucose through two processes(gluconeogenesis and glycogenolosis) as glucose is still needed for normal body function.