Olympic Sponsorships

Why is McDonalds an Olympic sponsor?  I mean, I know the pragmatic such a relationship exists: McDonalds has a lot of money that every national Olympic team could use and I'm sure the company enjoys all the prime advertising they get in exchange.  For all I know, there aren't very many other corporations that are willing to donate at that level.

But seriously, McDonalds?  McDonalds is the symbol of cheap, non-nutritious food to me (thanks to the film Supersize Me) and it seems highly incongruous to have the best athletes in the world using their achievements to sell products that would have a detrimental effect on their performance.  Athletes selling for Nike, Addidas, Spaulding, Speedo, all of these make sense to me.  Athletes selling deep-fried, high-calorie food?  

What's REALLY funny is that McDonalds has been a major Olympic sponsor for years and just now I'm catching on to this oxymoronical fact.