Protein is another major macronutrient that, like carbohydrates, consists of small repeating units. But instead of sugars, proteins are made up of amino acids. Proteins can be classified as either complete or incomplete. Amino acids from proteins form the building blocks for new tissues and the repair of body cells. They are also used for making enzymes, hormones and antibodies. Protein also provides a (small) fuel source for exercising muscles. Athletes have higher protein requirements than non-active people. Extra protein is needed to compensate for the increased muscle breakdown that occurs during and after intense exercise, as well as to build new muscle cells. The IOC and IAAF both recommend between 1.2 and 1.7 g protein/kg BW/day for athletes or 84–119 g daily for a 70 kg person. This is considerably more than a sedentary person, who requires 0.75 g protein/kg BW daily. Some athletes eat high protein diets in the belief that extra protein leads to increased strength and muscle mass, but this isn‘t true, it is stimulation of muscle tissue through exercise, not extra protein that leads to muscle growth. As protein is found in so many foods, most people, including athletes eat a little more protein than they need. This isn‘t harmful, the excess is broken down into urea (which is excreted) and fuel, which is either used for energy or stored as fat if your calorie intake exceeds your output.