I can't find the specific article I was looking for, maybe it's more urban legend than fact, but supposedly chess players burn just as many calories per hour as athletes. In the top results on google you'll find comparisons of chess players to football players, and chess grand masters to olympic swimmer Michael Phelps. Somewhere in here is material for an infomercial sure... play our specially designed MMORPG and the calories will magically melt away!