The starches are complex carbohydrates, polysaccharides, that are long chains composed of the simple sugars. Disacharides and polysaccharides need to be broken down enzymatically to be absorbed by the intestine. Carbohydrates have an energy yield of 3.5 kcal per gram. Protein is both an energy source an a source of amino acids. High-quality animal source proteins proteins provide superior digestibility, amino acid balances, and palatability.
Exercise increases an athlete s protein requirement.
Exercise places excess demands upon the body which result in tissue disruption and occasionally tissue damage. These tissues must be remodeled and repaired which can result in an increased protein demand. This demand can be met by increased protein ingestion. Protein can also be used for an energy source with an energy yield of 3.5 kcal per gram. Fat is used by the body for energy and can be used as a metabolic water source.