I am currently training for a marathon.. and have lost close to 15 lbs of nearly all muscle (my last bodyfat count before i started training was around 5%).. I anticipate losing probably 5-10lbs more before my race on Nov 30th..

My question: What is the best nutritional diet I can have *after* my marathon to bulk back up ? I do not want to do any supplements such as creatine or growrth hormones, etc.. I just want to know what I can eat (that I can buy at a grocery store) that will promote the fastest muscle growth..

protein, protein, and more protein. And working out correctly. Just make sure it is a good source of protein and not something loaded with fat.