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{{Skeleton}}There are three important ketones involved in [[Ketogenic Diet]]s. * '''Acetoacetic acid (AcAc)'''. AcAc is the ketone that is produced by the liver from fats and can be metabolized to provide energy. It could be considered the most directly useful of these ketones to the human body. However, AcAc lowers the blood pH, causing potential acidosis. AcAc spontaneously decomposes into Acetone (the half-life is 11.7 hours at 27c<ref name="HayBond1967"/>).* '''Acetone'''. Generally is often believed to be a waste product, but it has now shown to be metabolically active<ref name="Reichard-1979"/><ref name="Kalapos-1999"/>. It is excreted through the breath and urine, which can sometimes be detected as a fruity smell. Radio-tagged Acetone has been shown to be converted to glucose, fats and protein, but not other Ketones<ref name="Reichard-1979"/>. Acetone levels are one possible [[Ketogenic Mechanism of Action| mechanism of action]] behind the success of the [[Ketogenic Diets for Epilepsy]]<ref name="Kalapos-2007"/>.* '''Beta-hydroxybutyrate (BOHB)'''. Unlike AcAc, BOHB is stable and does not change blood pH, but it cannot be directly metabolized. AcAc is converted to and from BOHB in the liver and muscles, so BOHB forms a 'reservoir' of ketones that can be converted back to AcAc for providing energy<ref name="Musa-Veloso-2002"/>. (Technically BOHB is not a Ketone, but it's normally considered one.)

Ketones are used by most tissues in the body with the exception of those cells that have few or no mitochondria which and so are dependent on glucose<ref name="Westman-2003"/>.