Für die, die es aus der Feder von anerkannten Experten hören wollen:
Weight training causes little or no effect on whole-body leucine oxidation (104), suggesting that the use of protein as a fuel is not a consideration in this kind of activity. Thus, the question becomes whether resistance exercise causes an increased need for protein to allow remodeling of muscle. Because this kind of exercise is anabolic acutely, but training results in adaptation (see above), the conclusion is the same as that reached by Butterfield & Calloway; that is, exercise makes the use of protein more efficient, thus decreasing protein requirements, not increasing them!
In fact, eating more protein habitually leads to a rapid loss of body protein if the accustomed diet is suddenly diminished...
Quelle: Rennie, Tipton: Protein and amino acid metabolism during and after exercise and the effects of nutrition. Annu Rev Nutr. 2000;20:457-83.

Was man sonst noch über eine optimale Proteinzufuhr wissen muss, findet man hier: http://www.sportsnutritionsociety.or...-1-7-27-06.pdf

Siehe auch hier: Protein supplements and exercise -- Wolfe 72 (2): 551 -- American Journal of Clinical Nutrition

A strong theoretical basis exists for expecting a beneficial effect of a protein supplement in active people. Amino acid intake stimulates the transport of amino acids into muscle, and there is a direct link between amino acid inward transport and muscle protein synthesis. However, some experimental data suggest that exercise may actually decrease the protein requirements necessary to maintain balance. Nevertheless, it can be speculated that a protein supplement should be useful to stimulate net muscle protein synthesis, particularly if the supplement has the optimal proportion of individual amino acids.