"A ketogenic (keto) diet is high in fat and protein and low in carbohydrates. Most of the body's cells prefer to use blood sugar (glucose) as their main source of energy, says Harvard Health Publishing. The keto diet forces your body to use a different type of fuel. Instead of providing your body with glucose from carbohydrates, the keto diet relies on the liver to break down stored fat into molecules called ketones. (This process is called ketogenesis; that's where the diet's name comes from.)"