In the battle to lose weight, and keep it off, our bodies are fighting against us.
This is a great article that reports on some of the more recent studies on loosing weight. Pretty much all the standard "solutions" are out of touch with the reality that the body will fight hard to gain back lost weight.
We are going to need real science based pharmacological / genetic techniques to help folks who are already over-weight find a permanent solution. Diet and exercise can prevent obesity, but in reality can not permanently reverse it for most people.