A ketogenic diet is high in fat, moderate in protein and extremely low in carbs. As carbs are reduced and fat is increased, the body enters a metabolic state called ketosis. Then the body starts turning fats into ketones, which are molecules that can supply energy for the brain. After a few days or weeks on such a diet, the body and brain become very efficient at burning fat and ketones for fuel instead of carbs. The ketogenic diet also lowers insulin levels. This, along with the increased ketones, are two of the main reasons this diet has so many health benefits. Staple foods on a ketogenic diet include meat, fish, butter, eggs, cheese, heavy cream, oils, nuts, avocados, seeds and low-carb vegetables.