Ketosis is a metabolic state in which the body uses fat as its primary source of energy instead of carbohydrates. This occurs when carbohydrate intake is significantly reduced, prompting the liver to convert fatty acids into ketones, which can be used for energy by various tissues, including the brain. People often enter ketosis through low-carbohydrate diets, such as the ketogenic diet. In this diet, individuals typically consume high amounts of fats and moderate amounts of protein while limiting carbohydrates to induce and maintain this metabolic state.