Todd > If I eat ad libitum, even fully paleo foods, I'll hover at the
17-19% range, which is about where I am now.

Know what, though?  We have an unlimited food supply these days.  Perhaps
our ancestors did not and would occasionally have periods where food was
relatively scarce.  (Although I believe our omnivorous nature made
starvation relatively rare).  That would bring the body fat percentage
down.  My annual 3-day to 2-week fast seems a good way to recreate a
natural condition.