I, for one, am intrigued by the idea of a set point diet. The basic idea is that your body maintains homeostasis, and wants to maintain a certain weight. This is why, for example, if you lose the pounds, they come back. The idea is further that there is something in our environment -- in the food, or the air, or the water, perhaps -- that has ratcheted up the set point for many people (presumably depending on which genes they've expressed).

I know there's a book on the topic, and info on the internet. I don't know whether it works.