Mit "vor dem Training" ist nicht direkt vor dem Training gemeint, sondern so, dass das Whey zum Zeitpunkt des Trainings verdaut ist, also die Einnahme ist ca 45 min davor. Das bewirkt, dass die N-Bilanz während der ganzen Zeit positiv bleibt und man nie in einen katabolen Zustand kommt. Ansonsten wird die N-Bilanz negativ. Und der Grund dafür sind hauptsächlich die schnell verfügbaren und rel. großen Mengen BCAAs bzw Leucin (bei Whey). Jedoch sind auch die anderen ess. Aminos wichtig, denn nur BCAAs alleine können die N-Bilanz nicht positiv halten.

Darüber hinaus - und das ist hier wichtig - baut so ein Regimen Muskelmasse auf und Fett ab. Zumindest in Ratten:

"An Interesting study by Jean-Christophe, J., et al supports the argument that whey is the best source of protein for gaining or preserving muscle mass. In this study the lab boffins took a group of rats and made them exercise for two hours daily over a five week period. The rats were separated into groups one hour pre-workout and were either given a high glucose meal, whole milk protein, whey protein or fasted.

At the end of the five weeks body weight was greater in the glucose, whey protein and milk protein groups than the fasted group – not surprising. What is exciting is the fact that the whole milk and glucose group increase in weight was due to an increase in body fat. In contrast, the whey protein groups increase in weight was in the form of an increase in muscle mass and a decrease in body fat!

Due to whey’s ability to deliver amino acids extremely quickly during exercise only the whey protein group gained muscle mass and burned body fat. On a side not, this study (although not using human subjects) is in the favour of the ‘can you build muscle and burn fat?’ argument. "