Keto diet is based on a very low-carb way of eating that is designed to kick the body to burn fat. Ketones are small molecules made from fat, that the body naturally makes, and they serve as alternative fuel to sugar which is more commonly known as glucose. Ketones are made when you don't eat many carbs and an overt amount of protein. When the body is making these molecules, the body goes into a state called ketosis. By limiting the number of carbs and protein your body is forced to make ketones to sustain all the organs it supplies and get to the point where is basically runs only on fat.