The name ketogenic means that it produces ketones in the body. (keto = ketone; genic = producing) Ketones are formed when the body uses fat for its source of energy.
Usually the body uses carbohydrates (such as sugar, bread, pasta) for its fuel. Because the ketogenic diet is very low in carbohydrates, fats become the primary fuel instead. The body can work very well on ketones (and fats).
What foods are allowed on a ketogenic diet?
Foods that are generally allowed include high-fat meats, fish, oils, nuts, high-fat dairy such as cheese, and low-carb vegetables.
Unsurprisingly, reducing carb levels means cutting out bread, pasta, rice, and most conventional baked goods. However, achieving such low levels of carbs also means skipping legumes, root vegetables, most fruits and starchy veggies, such as potatoes. It is recommended that carbs are limited to 30g for men and 20g for women per day.