How does the ketogenic diet work?

When the body is deprived of external sources of glucose, the liver tries to release its glucose stores or to generate glucose through a process called gluconeogenesis. (Glucose can be stored in the form of glycogen in the liver and muscles.) These glucose sources, however, are only sufficient for a few days, and the body will eventually move to a new source of energy: fatty acids. Fatty acids are metabolized into ketone bodies (namely, acetone, beta-hydroxybutyrate, and acetylacetone), which are then used as an alternative energy source.^[1] This is how ketosis develops during the ketogenic diet, even in the absence of a caloric deficit. When ketosis is used as a tool to lose body fat or body weight, however, a calorie deficit is necessary.^[2][1]