As some of you know that another interest that I have outside of running is Economics, and not your supply and demand curve economics. More the economic approach to looking at and understanding why things happen. Not too many people do this better and with more interesting topic than Freakonomics authors Steven Levitt and Stephen Dubner.
Below is a link to a very interesting podcast that talks about obesity in America, and what incentives should there be for people to be more healthy. One of the ideas throw out is a tax on unhealthy food, which would help and certainly provide incentive to eat healthier food. However, for many runners like myself one of the big reasons we run is so that we can eat whatever we want. During the peak of my training programs and during ultra-marathon training I will burn 2,000-3000 calories a day just during my workout and potentially another 2000 throughout the normal days activity so for me there is no harm in having a double bacon cheese burger or two for lunch.
None the less I think it is interesting here is the link, they also have two great books out Freakonomics and Super Freakonomics which I highly recommend as well as their blog.