Ketogenic diet
Also known as: Keto diet
A ketogenic diet is a very-low-carbohydrate, high-fat diet designed to produce nutritional ketosis, a state in which the liver makes more ketone bodies for fuel. Carbohydrate is often limited to less than about 50 grams per day or 10% of energy, but the amount needed to sustain ketosis varies. Protein is kept adequate rather than eliminated.
Keto is a specific form of a low-carbohydrate diet; not every low-carb diet produces ketosis. It also differs from the carnivore diet, which does not require a particular fat-to-protein ratio or verified ketosis, because foods such as nonstarchy vegetables, nuts, seeds, avocado, and oils can fit keto. Nutritional ketosis is not the same as diabetic ketoacidosis, a dangerous condition caused by severe insulin deficiency.
Early body-weight loss often includes water released as glycogen falls. Longer-term fat loss still requires an appropriate energy balance, and a ketogenic label does not make calories irrelevant. Food choices determine whether the diet supplies enough fiber, micronutrients, unsaturated fats, and protein; a menu dominated by butter and processed meat is nutritionally different from one built around fish, olive oil, nuts, seeds, and vegetables.
For exercise, the 2024 International Society of Sports Nutrition position stand reports that ketogenic diets tend to produce similar maximal-strength and strength-gain outcomes to higher-carbohydrate diets, although some comparisons favor the non-ketogenic diet. Athletic performance overall is usually neutral or worse, particularly in elite endurance settings. Greater fat oxidation during exercise does not by itself mean greater body-fat loss.
Constipation, headache, fatigue, nausea, and reduced training capacity can occur during adaptation. People using insulin, sulfonylureas, or especially SGLT2 inhibitors need clinical guidance because carbohydrate restriction can change glucose-management needs and ketoacidosis risk; medication should not be altered independently. Pregnancy, a history of an eating disorder, and pancreatic, liver, gallbladder, kidney, or fat-metabolism disorders also warrant individualized medical advice before attempting keto.