Fasting has been recognized as a treatment for seizures since ancient times. The ketogenic diet is a low-carbohydrate, adequate-protein, high-fat diet that biochemically mimics the fasting state and has been used to successfully treat seizures for 85 years. The diet has enjoyed a resurgence in popularity over the past decade and is gaining acceptance and use worldwide. Many studies over the past several years have explored possible mechanisms of action for the ketogenic diet. This review addresses these studies, as well as recent research regarding possible indications for the diet, variations in its initiation, side effect profiles, and the recent use of modified formulations to improve tolerability.