Ketones are a type of organic compound produced by the liver when the body is low in available carbohydrate and raised levels of fatty acids are circulating in the blood. This commonly occurs during prolonged endurance exercise – e.g. a long, ride – or while adhering to a strict low-carb diet. Essentially, it’s a symptom of starvation. “During this state of ‘ketosis’, ketones are used as a fuel source by the muscle, brain and heart,” says James Moran, registered dietitian and performance nutritionist at Marylebone Health.
