As predicted, when I posted my challenge a few days ago, the anecdotal magic metabolism or two came out to play. There is certainly a cadre out there who believes:
VLC → lower insulin → faster fat burning metabolism
Some version of this is the purported Metabolic Advantage championed most prominently by Dr. Mike Eades. The nutshell version of this is that when you are low carb, excess fat consumed will be "blown off" through futile cycling and uncoupling. Despite admitting to eating a "starvation calorie level" diet himself, Eades perpetuates this myth of low carb magic.
What sparked this post, was a very well referenced post by Ambimorph over on PaleoHacks: Is lowered T3 resulting from a low carb diet problematic? She, along with another respondent on the thread, provides a long list of studies that show VLC lowers T3. Dr. Ron Rosedale (of Science Krispie Leptinade fame here at the Asylum) weighed in. He believes that this lowered T3 is a longevity-promoting benefit of VLC diets. Make no mistake, Rosedale advocates what Atkins referred to as a "biologically zero" carb diet - non-dairy protein and leafy greens. Lower T3 dials down your metabolic rate. This is seen as a good thing as stated by Andre Chimene in his answer: "having a fast metabolism is like idling your car at high RPMs... for your life." Additional comments bring up a good point: "You don't want your car idling roughly or stalling either." So this claim is:
VLC → lower insulin → slower efficient metabolism
What we have here folks is a contradiction in claims!
Those who boast over incredible weight loss/maintenance eating thousands of calories more on VLC are boasting over their exceptionally inefficient metabolisms. The Rosedales of the world are saying that's just not so -- VLC causes the body to move to a state of optimal metabolic efficiency. When your metabolism is supremely efficient, you have to eat less to maintain body weight. He and others contend that this is optimal for longevity. Rosedale is more correct than Eades here on the matter of metabolism. When it comes to what a ketogenic diet does to one's metabolism, lowering metabolic rate is where it's at. This appears to be a direct adaptation to "glucose deficiency".