# Ketone bodies

Ketone bodies are your body's backup fuel for when carbs run low. There are three of them. They are beta-hydroxybutyrate, acetoacetate, and acetone. Your liver makes them inside its mitochondria. The raw material is acetyl-CoA, which comes from breaking down fat (a process called beta-oxidation). They are more than fuel for your brain and heart, though. Beta-hydroxybutyrate also works as a signal. It blocks certain gene-silencing enzymes (class I histone deacetylases). It quiets an inflammation trigger (the NLRP3 inflammasome). And it may make your mitochondria run more efficiently. Those are exactly the effects that interest fasting and longevity researchers.

## Sources

- Owen OE, Morgan AP, Kemp HG, Sullivan JM, Herrera MG, Cahill GF Jr. (1967). Brain Metabolism During Fasting. Journal of Clinical Investigation. https://doi.org/10.1172/JCI105650
- Puchalska P, Crawford PA. (2017). Multi-Dimensional Roles of Ketone Bodies in Fuel Metabolism, Signaling, and Therapeutics. Cell Metabolism. https://doi.org/10.1016/j.cmet.2016.12.022

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