Abstract
Ketone bodies acetoacetate (AcAc) and D-β-hydroxybutyrate (βHB) may provide an alternative carbon source to fuel exercise when delivered acutely in nutritional form. The metabolic actions of ketone bodies are based on sound evolutionary principles to prolong survival during caloric deprivation. By harnessing the potential of these metabolic actions during exercise, athletic performance could be influenced, providing a useful model for the application of ketosis in therapeutic conditions. This article examines the energetic implications of ketone body utilisation with particular reference to exercise metabolism and substrate energetics.
Highlights
Ketone bodies acetoacetate (AcAc) and D-β-hydroxybutyrate may provide an alternative carbon source to fuel exercise when delivered acutely in nutritional form
In 1937, Krebs made arguably the most important breakthrough in biochemistry [1], describing a cycle of enzymatic reactions uniting dietary fuel combustion with cellular energy provision. This final common pathway for substrate metabolism has allowed the detailed study of the flow of energy transformation from dietary sources to the ‘energy currency’ adenosine triphosphate (ATP)
In a series of experiments in the 1960s, Cahill demonstrated the importance of cerebral ketone body oxidation in starvation, where up to 60% of the brain energy needs are derived from ketones, replacing glucose as its primary fuel [26,27,28]
Summary
Ketone bodies have long been overlooked as alternative substrates to power our bodies. Contrast between ketosis induced by starvation or high-fat diet (endogenous ketosis) and that generated by nutritional ketone ester ingestion (exogenous ketosis). Ketone bodies are endogenously produced in the liver from high circulating free fatty acids (FFA) from adipolysis. Nutritional ketone esters are cleaved in the gut and are absorbed through the gut epithelium and monocarboxylate transporters (MCT) into the circulation or undergo first-pass metabolism to ketone bodies in the liver. The evolutionary conservation of ketone bodies as energy substrates has a sound rationale, their being thermodynamic advantages to their oxidation, as well as the preservation of alternative energy reserves essential to our survival. Given the well-characterised demands of endurance exercise and the importance of dietary substrates on athletic metabolism, there is a clear rationale for the nutritional provision of exogenous ketone bodies in this context.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
