How the ketogenic diet works
In a standard Western diet, the liver primarily produces glucose from carbohydrates. When dietary carbohydrates are severely restricted, glycogen stores deplete within 24–48 hours and the liver begins producing ketone bodies (beta-hydroxybutyrate, acetoacetate, and acetone) from fatty acids. The brain and muscles can use these as fuel in the absence of glucose.
Individual ketosis thresholds vary—some people enter ketosis at 50 g net carbs while others require below 20 g. Protein intake must also be managed, as excess protein can be converted to glucose via gluconeogenesis and suppress ketone production.