Ingesting isomaltulose versus fructose-maltodextrin during prolonged moderate-heavy exercise increases fat oxidation but impairs gastrointestinal comfort and cycling performance

This study examined the metabolic and performance effects of ingesting isomaltulose, a slowly absorbed carbohydrate, during exercise. The results showed that isomaltulose increased plasma nonesterified fatty acid concentration and fat oxidation while decreasing carbohydrate oxidation compared to fructose-maltodextrin supplementation. However, isomaltulose ingestion led to severe gastrointestinal symptoms and negatively affected exercise performance. These findings suggest that isomaltulose may not be suitable for prolonged or high-intensity exercise compared to other carbohydrate supplements.