The shortest definition of peptides is this: short protein molecules. While normal-size protein molecules may consist of thousands of amino acids, peptides contain as few as two to 10 amino acids. Many protein products tout the fact that they contain high amounts of peptides because these smaller protein molecules are more readily digested than the larger protein molecules found in most whole foods or protein supplements. This means that peptides can get to work faster, building and repairing muscle tissue, making products with peptides a great choice after workouts or long periods without food (such as after sleeping) when your body needs protein as quickly as possible.