What is protein? How much protein do we need? Is it possible to eat too much protein? These are important questions for people following a low-carb way of eating, who usually are replacing part of their carbohydrate intake with protein.
Another way to compute protein needs has to do with lean body mass, rather than total body weight (based on the idea that our fat tissue needs less protein to support it). This method is discussed in the Zone Diet and Protein Power books. The second calculator on this page can help you compute this number. To do this, you will also need to know your body fat percentage. (Body Fat Calculator here)
Where this falls down is when people are eating diets that are lower in calories for any reason, conscious or not. People who are ill or losing weight, for example, do not need less protein just because they are eating fewer calories -- so anyone on a weight loss diet shouldnot go by the "percent of calories method" for calculating protein needs.
Extra protein can be broken down into glucose in a process called gluconeogenesis. On low-carb diets, this happens continually. One benefit of obtaining glucose from protein is that it is absorbed into the bloodstream very slowly, so it doesn’t cause a rapid blood sugar increase. However, some diabetics do find that too much protein causes an excessive blood sugar rise, and low-carbers sometimes find that as time goes on they do better with a moderate protein intake right than eating large amounts of protein.