Exogenous ketone

Exogenous ketones are a class of ketone bodies that are ingested using nutritional supplements or foods. This class of ketone bodies refers mainly to β-hydroxybutyrate [BHB]. The body can make BHB endogenously, via the liver, due to starvation, ketogenic diets, or prolonged exercise, leading to ketosis. However, with the introduction of exogenous ketone supplements, it is possible to provide a user with an instant supply of ketones even if the body is not within a state of ketosis before ingestion.

Most supplements rely on β-hydroxybutyrate as the source of exogenous ketone bodies. It is the most common exogenous ketone body because of its efficient energy conversion and ease of synthesis. In the body, BHB can be converted to acetoacetic acid. It is this acetoacetic acid that will enter the energy pathway using beta-ketothialase, becoming two Acetyl-CoA molecules. The Acetyl CoA is then able to enter the Krebs cycle in order to generate ATP. The remaining BHB molecules that aren't synthesized into acetoacetic acid are then converted to acetone through the acetoacetate decarboxylase waste mechanism.