Protein deficiency happens when your body doesn't have enough protein or essential amino acids. Protein turnover is the balance between making and breaking down proteins. Having more protein synthesis than breakdown builds lean tissues, while more breakdown than synthesis burns lean tissues. The amount of amino acids in your blood doesn't always match how fast they're broken down. Eating too little or too much protein can change how fast amino acids are broken down. Protein deficiency can be caused by not eating enough protein or by certain health conditions. Treating protein deficiency involves eating a balanced diet with enough energy, protein, and nutrients.