Abstract: A unique, chemically-defined nutrient composition is disclosed which can enable stressed, catabolic, marathon athletes to achieve superior performance. The diet provides substantially all of the essential nutrients along with flavoring aids in simple, readily available form and comprises free amino acids, vitamins, minerals and trace elements, electrolytes, simple and complex carbohydrates, and flavoring aids. This diet benefits athletes because it provides for substantially all of the nutritional requirements, allows for reproducibility and user familiarity through precise chemical definition, supplies optimal nutritional requirements during training and competition through unique tailoring to the nutritional requirements of an individual athlete, requires minimal digestive energy, and encourages maximal absorption of nutrients. A specific mixture of amino acids, carbohydrates, and flavoring aids is used to achieve superior taste.