I would have to say from my experience using them, and all that I've read about them, that intermittent fasting diets are marvelous.
In regards to the post above, when I IF I don't skip meals a vast majority of the time and I am never hungry/unsatisfied. Check out the introductory/about articles at leangains.com for some very great info on intermittent fasting protocols. I very much like his recommended 8 hour feeding protocol. Haven't heard complaints about it.
Also, from an evolutionary standpoint food would have been in constantly varying quantities, and if an 'energy conservation' state existed as described it would have been active almost all the time, but primitive hunter gatherers were almost always relatively lean and disease free. Supposedly at low levels of body fat (6-10%/can see your abs) your body still has MONTHS worth of ketones to use as energy in the form of your stored body fat.
Side thought: I've heard reference to studies that some amount of cellular repair gets activated only in times of fasting.
I've just read the Four-Hour Body by Timothy Ferriss. It seems on the face of it like ridiculously valuable material, if true - like what the completed version of Michael Vassar's proposed reboot of dietary science would look like at the finish point if dieting turned out to be more susceptible to Munchkinism than in my wildest dreams. Ferriss also talks the rationalist talk quite well in this book, much more so than in Four-Hour Workweek; he cites the experiments and occasionally says things like "I spent a lot of money on this and I expected it to work and it didn't work at all" or "I tried this and it seemed to work and I have no idea why it worked and I think it was probably a placebo effect."
Does the LessWrong hivemind have an opinion about 4HB? Has anyone tried it and found that it doesn't work, or that it does work, or that it works but not as well as Ferriss thinks it should work?