One of my favorite writers on human genetics, Razib Khan, runs across an Art Devany interview and gives his interesting two cents. In a nutshell, Devany considers endurance sports and running in particular to be a form of arch-villainy. More on Devany is here. Note that Khan makes the same point I did: let's see how it works within related individuals (Devany looks to be in good shape in those pictures. Did a lot of his relatives struggle with early-life obesity? I doubt it.)
Devany is an economics professor, which means he must know his statistics - so he should know that in statistics, you can't ask too many statistical questions with the same set of data. Why? Because if you ask enough times, eventually, there will be an equation that fits the scatterplot you're looking at, purely by accident. The converse applies as well. The further afield a theory is applied, the more likely it's not giving us real information, beyond the overconfidence of the theorist. The guy who created the Simpsons (Matt Groening) had a comic called Life In Hell, and I remember one of them was a list of types of college professors. One of them was called the One Theory Explains Everything Guy: "The nation that controls magnesium controls the world!"
On a podcast I heard from December 2009, paleo promoter Robb Wolf extended his claims for a paleo diet from weightlifting performance (I have no grounds on which to object) to "leaky gut" (a "syndrome" incoherent enough that it's not medically recognized) to claims that Huntingdon's disease (yes, really) could be treated by moving to a paleo diet. For the record: Huntingdon's is a well-understood genetic neurodegenerative disorder - you get it from your parents, not from grains.