A keto diet is low in carbohydrates and high in fat. And the idea is simple. You switch the body’s fuel from sugar to fat. Our bodies normally utilise glucose (sugar) to produce energy. Whenever blood sugar depletes, for instance during and after sport, fasting, or starvation, the body shifts to fats as a source of energy. As with prolonged starvation, the keto diet puts the body in a state called ketosis — that’s when the body runs on fat. The name comes from “ketone bodies,” which are fat-derived compounds that the body relies on for fuel in the absence of sugars. When you limit sugar intake drastically, you force your body to use all the stored glycogen, a form of sugar stored in the liver. And when that sugar is used up, the body turns to burning fat for fuel and, after a period, enters the ketosis state. It can take 2-4 days to enter ketosis.