During the 2008 Beijing Olympics, much was made of Michael Phelps' alleged 12,000-calorie-a-day training diet. ("Never had that been true!" Michael protested recently on Twitter...and he has admitted he doesn't eat that monumental amount of food as he's training for this year's Games.) Hype aside, there's no question that Olympians require special fuel to keep them training and competing at the optimal levels required for international sports competition.
As recently as a few decades ago, Olympic athletes were bound by rules of competition that forbade them from making money from their sport, part of the International Olympic Committee's commitment outdated ideal of an amateur athlete. Those rules were phased out starting in the 1970s, and now we have gone so far in the other direction that many Olympic athletes now pull millions of dollars from endorsements. Off the top of my head I can think of Michael Phelps, Lolo Jones, Hope Solo, Marlen Esparza, Nastia Liukin, and Ryan Lochte.