Hi Micro, there needs to be a single window. I'd suggest noon to six PM for most people, as it allows you to catch a late lunch and an early dinner (for social connection). Or maybe 2pm-8pm, if that fits better.
The critical "ingredient" for the body is experiencing actual HUNGER - which cannot be immediately sated. This forces physiological pathways in the human body to switch on which cause things like fat stores and gluconeogenesis (production of sugar from liver) to occur. It causes insulin and insulin-related hormones to shut off (you might want to glance at this on insulin and aging: http://pubmed.ncbi.nlm.nih.gov/18948730/ ).
It turns out that recurring, actual periods of HUNGER are critical to triggering the body systems to run properly and even to trigger apoptosis (killing of defective/pre-cancerous and other disease) cells. http://en.wikipedia.org/wiki/Apoptosis
Much of this has been known for the better part of a hundred years. Other portions, such as how systems interlinked and what, exactly, were the necessary components have only been worked out in the last thirty years or so. Doubtless, there is more to figure out, but what has been figured out - the critical role of periods of HUNGER (which your body takes as famine or threat of famine, and a trigger to start being more efficient with calories) - won't be overturned...it isn't a "fad".
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