The source explores the science of sugars in endurance sports, focusing on how the body processes carbohydrates for energy during prolonged athletic activity. It discusses the breakdown of carbohydrates into simple sugars like glucose and fructose, highlighting their respective roles as fuel sources. The article also addresses common gastrointestinal issues experienced by endurance athletes and introduces strategies like gut training to mitigate discomfort. Furthermore, it examines various types of sugar-based fuels, including traditional gels, modern hydrogels, and highly branched cluster dextrin, evaluating their effectiveness in providing sustained energy and reducing digestive distress during high-intensity, long-duration events.