I think the African runner's diet is pretty interesting. It looks like a good way to get some insulin resistance to me, but they exercise enough that, at least in the short term, this doesn't seem to be the case. Noakes spends a good bit of time talking about them in some podcasts I've listened to. Being from South Africa, he gets the opportunity to work with athletes from all over Africa. Anyway, he thinks it's somewhat of a self-selective process. All of them eat in the same way and the ones that can process that food the best are the ones that become the most successful. It doesn't necessarily mean that this is the best diet, rather, this is the diet that the best eat. Those are not necessarily the same thing.
It also shows that different people need to fuel themselves differently based on their goals and genetics (possibly epi-genetics).