Ketosis is a metabolic state in which your body uses fat and ketones rather than glucose (sugar) as its main fuel source. Glucose is stored in your liver and released as needed for energy. However, after carb intake has been extremely low for one to two days, these glucose stores become depleted. Your liver can make some glucose from amino acids in the protein you eat via a process known as gluconeogenesis, but not nearly enough to meet all the needs of your brain, which requires a constant fuel supply. KetosisNow Review