The Ketogenic diet is a diet based on low carbs and high fat. This diet involves drastically reducing carb intake and replacing it with healthy fat. The reduction in carbs and replacement of it with fats allows your body to go into a metabolic state called ketosis. Ketosis is a process that occurs when your body doesn't have sufficient carbs to burn for energy. So instead, it burns fat and makes things called ketones, which it can use for fuel. So, in short, this diet causes ketosis which is when your body uses your fat for energy.