as usual, pklopp nails it. this is why when people talk about a fat burning metabolism, vs. a sugar burning metabolism, it's crapola. you can have a fat-based diet or a sugar based diet, or a combination of both, but your metabolism does not change - it just burns whatever fuel is available.
"dean ornish and dr. davis think the palmitic acid our bodies use for fuel while we sleep is poison if we eat it. zero-carbers like charles washington think the oldest fuel in our evolutionary history – glucose - used by organisms a billion years ago and without which the brains of modern mammals cannot survive for more than a few minutes – is an unnatural toxin if you eat it. both views ignore basic facts of medical physiology and defy evolutionary history." - kurt harris