Ketogenesis is a metabolic process that occurs in the liver when the body lacks sufficient carbohydrates for energy. During this process, fatty acids are broken down into molecules called ketone bodies, which can be used as an alternative energy source by various tissues, including the brain. This process typically happens during periods of fasting, prolonged exercise, or low-carbohydrate diets, such as the ketogenic diet. Ketone bodies provide a more efficient energy source than glucose, helping to maintain energy levels when carbohydrate intake is low.