Eating too much protein and not enough carbohydrates.
The “low or no” carbohydrate diets are very popular and many people try to replace carbs in their diet by high protein foods. But carbohydrates are essential as they have PROTEIN SPARING ACTION.
The main function of the carbohydrate is to provide energy and the main function of protein is growth, building, repair wear n tear and thus maintain the body. But if sufficient amount of carbs are not consumed (like high protein low carb diet) proteins are used by the body for energy purpose. Proteins might be an expensive source of energy as compared to other energy sources such as carbohydrates or fats.
So, adequate amount of carbohydrates in our diet supplies required energy to the body and thus proteins are spared for muscle building and repair rather for energy purposes.
Athletes cannot go on low carb, high protein diet as there are chances of losing lean body mass. Since carb will be low , amino acids will be used to provide energy. Hence in their diet carb form an essential component which will spare the protein to help in building and repair of muscles.