For over 40 years, Professor Clarke has used magnetic resonance (MR) imaging and spectroscopy to measure the effects of diet on energy metabolism in human heart, brain and skeletal muscle. This work led to the development of a fourth food group, a ketone ester called deltaG, which improves physical performance and cognitive function and could be used for the management of common metabolic diseases, such as type 2 diabetes, heart failure and Parkinson’s disease. In 2005, following a successful application for Defense Advanced Research Program Agency (DARPA) funding of $10 million to invent a food for soldiers on a battlefield, Professor Clarke founded the University of Oxford spin-out company, TdeltaS Ltd. The company was set up to research and commercialise the ketone ester, deltaG. The names of the company and the ester are based on the thermodynamic equation for Gibbs free energy: ΔG° = ΔH° - TΔS° which defines the energy available to perform work. Since 2005, the company has filed 25 patents and 18 trademarks in over 40 territories around the world. More than 40 research papers on deltaG have been published in high impact scientific journals and deltaG has regulatory (FDA) approval in the US for the military and the public. Following the development of methods to produce deltaG at scale, over 20 tons of the ester have been sold in the US since early 2018.