It's an understandable mechanisms that other animals may use to survive tough conditions (e.g. bears and hibernation, or any animal that hibernates and lives off its own fat in the winter, etc). The thing with this factoid is that fatties re-interpret it to the extreme to the point where their claims become bogus excuses. "Starvation mode" is a myth but the mechanism wherein starvation can slow metabolism is not untrue either. It's not as simple as fatties try to make it out to be. I mean, no one argues that starvation increases metabolism or that metabolism stays the same when you truly starve. Most people agree that metabolism is affected in some way when you deprive your body of food. Again, this doesn't mean "starvation mode" as it is used by fatties/pop culture/diet claims is true though.  http://www.tpnteam.com/secure/starvation_metabolism.html