1. A LCHF diet prevents the metabolic rate from decreasing under calorie restriction?
“…How many published studies from well designed, prospective human trials have shown that impaired thyroid function (i.e., hypothyroidism) occurs on a ketogenic diet? The answer to this question is quick and simple – NONE!
2. A LCHF diet is capable of burning fat in the absence of calorie restriction?
Ibid.
Nick, sorry I missed this when you posted it. Quite a read there - heavy going, as it were. 
I come away from it not too worried about metabolic rates - whether we stay the same on a per kilogram basis or if the body adapts and slows things down some. I’m very interested in what you say about ‘metabolic ramping’ - I hope you post what you and your crew find out.
The report did have some surprises for me.
obese humans and animals subjected to prolonged starvation die after depletion of body proteins and death may be independent of the availability of fat for oxidative metabolism. This suggests that substrates other than acetate derived from fatty acid oxidation are essential for maintaining energy requirements for vital functions.
This is more of a mixed picture than how I previously thought of things, i.e. while indeed some autophagy is going on, using protein in the process, we almost entirely live off our own fat while fasting - it we have enough of it. The report says some protein is being used all along, and has to be, even if large fat stores are present. So I wonder - is the recycling of autophagy enough of a protein supply?
Yup. In the mainstream press we hear that fasting is starvation and burns muscle. The fasting enthusiasts tell us that fasting causes autophagy the eliminates wonderful things like loose skin and old scar tissue. Both parties are referring to the nebulous “lean mass” that is lost during these experiments. They’re both partly right.
I don’t think anybody has any idea precisely what “lean mass” tissue is consumed during a particular fast. We do know that some tissues are more protected than others. The heart muscle for example seems to be poorly protected from autophagy during fasting, which we know because people die as a result and the autopsy reveals it. I don’t really consider that superfluous tissue autophagy!
One thing that is for sure is that the “lean mass” autophagy accelerates as a function of obesity. The fatter you are, the less lean mass autophagy you get. This is not what anybody wants to hear. The fat people want all that loose skin gobbled up, and the skinny people don’t have too much loose skin to lose so they know it’s not that, and they don’t want to lose muscle. Take a look at this chart from Elia et al, the whole study is definitely a worthwhile read. Dr. Fung says you won’t lose much muscle during a fast and places the caveat “if you’re 300lbs”. That’s a very important caveat. The study is linked below the pic.
https://onlinelibrary.wiley.com/doi/epdf/10.1002/j.1550-8528.1999.tb00720.x
Nick, it makes sense that leaner people would have to get a higher percentage of energy from non-fat sources while fasting, particularly if we subscribe to the ‘limit of fat we can access per day.’
This is puzzling to me. I’ve read that even in the case where the person has literally starved to death, the loss of heart muscle is very low. Right now I can’t find where I read this, but there was a Russian study of people who had died that way, and the loss of heart muscle averaged only 3%.
If prolonged fasting endangers the heart, that does not seem to jibe with the known cases of very long fasts, from what I’ve seen, up to good old Angus Barbieri and his 382 day fast. Toward the end of his fast, he was given potassium supplements - I assume for potential blood pressure and heart concerns, among others.
Interesting! Maybe I’m overstating that bit then. I recall reading that heart damage was the cause of death for a number of fasting patients in the 70’s and that was partly what ended it’s use as a therapeutic treatment (granted they were not in good health to begin with). I don’t have any hard data or studies. It’s probably not fair to say based on this that the “heart muscle is poorly protected”. If you have studies that say the heart is largely unaffected (3% loss), I’m happy to say that I was misinformed because I really enjoy fasting! 
Still, the larger point stands, we don’t really understand exactly what tissue is being consumed by autophagy. My guess though is that if you’re sub 20% bodyfat, and you’re getting 500kcal/day of energy from your own protein, it probably ain’t all cellulite & wrinkles!.. 
Yeah, this is it - where all is it coming from - that’d be around 125 grams or 4 to 5 ounces. Our skin is about 1/6 of our total weight - that would go a long way. Once autophagy is up-regulated, differing amounts of consumption of cell parts and proteins in cells occur, as well as an increase in the outright death and recycling of whole cells (and of course it’s rarely that simple - autophagy also “rescues” some cells from death… 
) - and the longer increased autophagy proceeds, it can go too far, all other things being equal, where the inner parts of the cell are affected to such a degree that the cell may die - there’s a term for it - “autophagic cell death” - so it’s a real deal.
Maybe things are not equal, there - at that point, getting rid of the cell may be in the body’s best interest…
I was wrong about the heart thing. Although it does appear that heart complications were a leading cause of mortality back in the age of therapeutic fasting 1950’s-1970’s, it wasn’t at all what I thought. It looks like the majority of cases involving heart failure involved liquid protein supplemented fasting! In other words, the “fake fasts” accounted for the majority of deaths during extended fasts recorded in the literature as of 1982. Also the cause of death wasn’t impairment of the heart due to autophagy, but seemed to more of a heart regulation thing “prolonged QT intervals”.
This journal article on the history of therapeutic fasting is an interesting read. The bits about fasting complications and mortality is on page 395.
That is a relief. Thanks for correcting the record.
