Ketosis, or ‘Keto’, is a natural state for the body in which it becomes almost completely fueled by FAT through eating a Ketogenic diet: low carb, moderate protein, lots of healthy fats. As babies, we are all born in a state of ketosis and remain that way until we begin eating solid foods (breast milk is almost entirely fat!) We also dip into a state of ketosis when we enter prolonged periods of not eating, or fasting, including while we are asleep. It is highly likely that you wake up in a ketogenic state!
While in ketosis, the body is producing ketones. These small molecules are used as fuel when we have depleted our glucose (blood sugar) supply. Ketones are produced in the liver, from fat, as we eat very few carbs and a moderate amount of protein. The entire body – including the brain – consumes ketones as fuel.
Fun fact: the brain can ONLY run on one of two fuel sources: glucose or ketones. It’s a common misconception that the brain needs carbs. The truth is that carbs are the single macronutrient (there are three: protein, carbs, fat) that we do NOT need, and the brain will happily burn ketones for fuel.
Those of us who follow a ketogenic lifestyle switch our fuel sources back to the way we were born; we run almost entirely on fat. Insulin hormones dip to low levels and we rapidly burn stored fat for fuel. Outside of weight loss, we ketonians experience sustained energy, mental focus, exercise endurance, and a bevy of other health benefits such as disease prevention and treatment.