Fortunately, protein is not normally used up for energy when adequate levels of carbohydrates and fats are present. When you do, your rate of protein synthesis equals your rate of degradation. If you don't consume enough calories and proper amounts of amino acids from the protein in your diet, you can go into negative nitrogen balance. This means your body can become cannibalistic and actually break down the protein in your own muscle tissues. This happens when you restrict calories too much, especially when you limit your intake of protein too drastically.
Protein is the body's main source of nitrogen, and when it breaks down, nitrogen is excreted.
By measuring the amount of nitrogen excretion, we can tell how much protein is breaking down. When more nitrogen is being eliminated than is taken in, you are in negative nitrogen balance and your muscles are literally wasting away. It is critical to prevent this, especially during weight loss and body building. Considerable research has also shown that supplementing with these readily-absorbed amino acids can provide valuable benefits to older patients in nursing homes and ailing individuals confined in hospitals. Calories are not used up in fat tissue.