Also - why is there the assumption that Nitrogen loss is definitely protein loss? It seems misleading. Where’s the science saying this is definitely muscle loss?
How is 300 kCal/day considered fasting? All the fast studies referred to were supplemented fasts.
Sorry there are just so many questions!
Indeed - I thought of this at the mention of the ‘Minnesota Starvation Experiment’ - this was just calorie restriction. This was not fasting.
I question even this, Ross. Anecdotal, but I was never even remotely keto-adapted until this year, and had fasted for two days quite a few times (just the way things worked out) and once for six days in 1981, and didn’t feel anything “bad” at all. Okay, somebody is a carb-burner. They fast, their blood glucose goes down, their glycogen stores get depleted, and then they start the adaption to burning fat. What, really, is the harm?
Hi Doug!
Good question.
My limited understanding is that prior to being fully fat adapted, our bodies only have limited access to the energy in our stored body fat so the body is likely to respond by reducing metabolic rate to match reduced available energy.
Post adaptation, we have access to nearly unlimited energy (FASTER study showed mind-blowing fat oxidation rates) so the body has no reason to reduce metabolic rate…might even crank it up a notch.
I think the parable of the blind men touching different parts of an elephant is illuminating here.
Phinney and Volek have studied different patient bases than Fung. It is expected they would have different results and therefore arrive at different conclusions. A middle aged, obese T2D and a college aged athlete with 15% bodyfat are not likely to respond to interventions similarly. If the former does prolonged fasting, it is likely to improve their health on every front. If the latter fasts for extended periods of time, they will likely lose muscle.
Long term fasting isn’t for everyone. It’s a drastic intervention for people who have severely deranged metabolisms. And like all medical interventions, there are risks associated with it. But in the appropriate cases, the risk may be worth it.
Someone who has good biomarkers and just wants to lose 20 lbs can achieve that with IF, there is no need for extended fasting. Someone who is insulin resistant and 100 lbs overweight may need to fast for longer periods of time.
Both scientists are right. It’s a matter of which protocol is appropriate for you.
I think Phinney and Fung can both be mostly right at the same time. The body’s protein is consumed during extended fasting, including lean muscle mass, but we’ve evolved to do this in a fashion that has minimal impact on long term health and is likely beneficial for most people except in extreme cases of starvation.
Consider the n=1 fairly extreme example of actor Christian Bale who in preparation for the movie “The Machinist” for 4 months went on a near starvation diet of just an apple or a can of tuna a day and dropped from nearly 180 lbs to between 110-120 lbs. In several scenes the camera dwells on his emaciated frame and his muscle loss was such that he said the running scenes were very difficult. But two years later he is playing Batman with a body fit for the role. He clearly didn’t fear the dangers of fasting induced muscle loss and was apparently able to reverse whatever damage was done. He’s undertaking a new scarier to me challenge of a role playing Dick Cheney and he’s eating a lot of pies in preparation. I hope the recovery goes as smoothly as it did for the near starvation.
I am not sure we know enough about autophagy to say it works almost exactly like the protein we ingest in repair processes. I’m hearing that people are claiming they are interchangeable, as in, “If I don’t eat protein the by products of autophagy will provide the materials to do the work dietary protein does.” I’m skeptical about autophagy being a kind of panacea. That said, I think there are drawbacks to extended fasts people in the keto community don’t always want to talk about, especially the psychological of engaging in longer fasts for extended periods of time. I think it’s prudent to no place too much emphasis on any one mechanism as being the end all be all for resolving health issues.
Erin, I’d think that it would work well - the amino acids required for human life are what went into the protein structures that are being recycled and broken back down into amino acids. Everything necessary should thus be there.
Totally agree. (For one thing, all this thinking about fasting, diet and food is making me almost achingly hungry. 
) There is a woeful lack of research and knowledge about it, to be sure. At the same time, trials are being done on drugs that start autophagy in the body, due to their promise of being cancer treatments, etc.
I’d be interested in hearing about those drawbacks. Never have heard any. I know that fasting isn’t for everybody - plenty of tales like “I got to that second day and said the hell with this!” Yet I think you are talking about longer-lasting things that persist after one begins eating again.
This is true - I suspect that in other than extreme cases (true starvation, or intended weight loss well beyond just losing unneeded fat) - most people are just fine, and for a long time, while fasting.
I respect Dr. Phinney, but he himself has admitted that he is biased against fasting and has never really studied it besides looking at existing literature.
I’ll go with Fung who actually has clinical experience with it.
Most likely it is, though there could be another explanation. However, protein loss is not the same as muscle loss. There are lots of tissues made up of protein that are not muscle and become redundant when weight is lost – skin and connective tissue for example.
Also, Phinney doesn’t acknowledge that because of the increase in growth hormone, the body rebuilds needed tissues very quickly after the fast ends. That’s an important point that is often forgotten.
Finally, experiments with dogs that I came across in a Soviet book on fasting showed that even at death, when all fat was gone and the body had started cannibalizing itself, vital organs like the heart were still practically untouched at only 3% loss of mass. Other organs less immediately vital had more loss, but it shows that the body is not stupid (like Dr. Fung likes to say).
I agree as well. Sure protein loss occurs with fasting. I am hoping the excess protein in my excess skin goes away soon
It is also worth pointing out that people do not carry around ‘extra’ protein stores held in reserve doing nothing — just waiting to fill in for the day we don’t eat enough dietary protein.
There is a small storage reservoir of protein in the body called the labile store of protein, which is roughly 1% of our total lean mass. But it’s not in a purely storage molecules like triglycerides, glycogen, or betahydroxybutyrate (respectively storing fatty acids, glucose and acetoacetate), it’s mostly protein structures deployed for uses that can be easily redeployed … eg: circulating lipoproteins like albumin, and LDL, and old tissue just waiting for a quiet period to undergo normal apoptosis.
We also have the ability to make many amino acids from metabolic raw materials, reclaiming nitrogen from circulating levels of urea. So in the initial days after a fast our net nitrogen loss will be reduced as we become nitrogen sparing.
- Rabast et al, 1981.
Total fasting was compared with a 300 kcal/day very low calorie diet providing 56 g protein and 12 g carbs in 14 healthy obese patients, selected as matched pairs, over a period of 28 days. The weight loss was significantly greater during fasting than during the VLCD (16.5 kg vs. 12.7 kg). The basal metabolic rate showed a significant decrease (25 per cent) during total fasting, but was unchanged with the VLCD.
Dr Phinney is right that healthy obese people who fast for 28 days have been observed to eventually see a 25% reduction in resting metabolic rate [ https://www.ncbi.nlm.nih.gov/pubmed/7275468 ]. I suspect a lean person who fasts would see something similar after their circulating elastic capacity is drawn down - say after an 18 hour fast.
A type 2 diabetic with adequate body fat reserves who fasts may well have a greater energy surplus, as their access to their stored energy is no longer constrained by elevated insulin. I’d like to see some metabolic cart studies into fasting subjects (lean insulin sensitive, and overweight insulin resistant) and put some real data and contexts on this question of what happens to your resting metabolic rate when you fast and how that changes over time.
Is Dr Fung correct that metabolic rate increases over the first few days to increase the likelihood of a successful hunt? And is Dr Phinney correct that the body adapts over longer periods to become energy sparing?
I didn’t know about [ https://www.ncbi.nlm.nih.gov/pubmed/2104036 ] which suggests based on Dr Phinney’s interpretation of his own study that a protein level of 1.5 g/kg is more protective of function than 1.2g/kg
Compared to baseline, VO2max and peak quadriceps strength declined on the 1.2 g/kg protein dose, whereas both of these functions were preserved at the 1.5 g/kg level.
I found it interesting that the lower protein arm also had 3 times the carbohydrates of the higher protein arm (30 vs 10g/day) and while the statistical significance for the results of the lower protein higher carb arm were just significant (VO2 max 2.44 - 2.06 l/min) the results for the higher protein lower carb arm were just below the level of significance (2.16 - 2.01 l/min). With the carbohydrate confound and the closeness of the results I suspect his interpretation may be a little generous to his narrative.
The amount of lean tissue you have is a strong determinant of your resting metabolic rate. Interpretation: your total muscle mass is your furnace – the more muscle you have the faster you can burn energy.
Interestingly Dr Phinney did one of the experiments that shows that resting metabolic rate is dynamic and determined by energy budget (which will include supplying energy to lean mass). [ http://www.metabolismjournal.com/article/0026-0495(88)90011-X/abstract ] Where he locked 12 obese women in a metabolic ward, fed them slightly hypocalorically so they were under modest energy constraints - then had half of them run on a treadmill up to 2 hours, and the others just sit on the couch watching TV. After 5 weeks he weighed them and the couch potatoes lost a non significant amount more weight because the exerciser’s metabolic rates were down regulated for the 20 hours in the day when they were not on a treadmill to account for the increase in exercise demand for energy.
In general I agree with Dr Phinney that not getting adequate protein is a serious problem. He mentioned to me when he was in Sydney recently - In the 1970s there was a liquid protein fast (basically jello shots) that was nutritionally inadequate and killed several people but because they coincidentally get people into a state of ketosis - THAT damaged the reputation of ketogenic diets for decades and dried up all funding right at the most important phase of his career. So I get why he is concerned. He’s too old to have to go into the wilderness for 4 decades again.
But there is also the problem of diets that advocate unsafe levels of too much protein. There are plenty of people around the internet recommending eating 4.4g/kg LBM and up … and there is research [ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC333026/ ] showing that healthy people can only deaminate about 3.31g/kg LBM of protein a day before they saturated their ability to dispose of the ammonia … and that has killed 2 people in 2017 alone.
This is why I believe that Ketogenic diets should actively avoid being associated with high protein fads. Diabetics who need the option of ketogenic diets to reverse their disease also can not go back into the wilderness for 4 decades.
I am old enough to remember the liquid protein diet. My dad went on it, lost a lot of weight, became quite ill and later developed myasthenia gravis. Who knows if there is a correlation? Nevertheless, I have seen people become quite sick from an overabundance of simple carbohydrate, less so from an overconsumption of protein and none from not consuming enough protein.
As @richard notes above, it’s far from that simple. Surely, this is a place where hormones/thryoid stuff comes into play. There’s also a common idea that muscle tissue burns more calores than it actually does. Over the years I’ve seen a bunch of posts, blogs, etc., claiming stuff like “each pound of muscle burns 50 calories per day.” Ha, I wish!
Muscle cells are definitely more metabolically active than fat cells, burning about 7 calories per day per pound, versus roughly 2 for fat cells. So we have a net difference of close to 5 calories per day per pound. (Quoting from livestrong.com, “In one study that examined 468 men and women and was published in a 1985 issue of the “Journal of Applied Physiology,” researchers determined that men had an average of 72.6 pounds of muscle compared to the 46.2 pounds found in women.”)
Using these figures, putting on 10lbs/4.5kg of muscle will thus mean an additional 70 calories burned per day. Losing 10 lbs/4.5kg of fat and adding the same weight in muscle means an additional 50 calories burned per day.
I don’t know if this is relevant but there is a famous French documentary about long fasting as medical treatment. Here is an article in English about it.
As Gary Taubes has shown it in his books, the science of nutrition and the understanding of obesity were far more developed in Germany pre World War II and all the results were lost after the defeat of Germany. It seems that the same thing happened with therapeutic fasting : the practice was developed in Russia by the Dr. Yuri Nikolayev but due to the Cold War, all the medical articles were muted in the “West”.
Moreover another medical practice was lost during the Cold War : virus phage therapy. Pre World War II, antibiotic and phage therapy were developed at the same time. After the war, antibiotics prevail but phage therapy was still used in Russia and nowadays their scientists are leading the research in this domain.
Here is the website of the Buchinger Wilhelmi Clinic. I can’t find more informations about their protocol but they seem to use fasting for all kind of treatment. The clinic has been featured in a French article here and the Dr Wilhelmi de Toledo has written a book about therapeutic fasting : L’Art de jeûner.
I love 2KetoDudes and all the experts of the Obesity Code podcast. But, I think that English speaking community should look more in the direction of other langage communities (German, Russian, French…) in order to foster the Keto/LCHF lifestyle and studies.
(I hope that my broken English is comprehensible ^^, I’m French)
I found your last line quite funny because I was internally complimenting your writing as I read.
Great post. I look forward to reading through the material you linked to.
Feed a cold, starve a fever? Sometimes, old wives tales have a nugget of truth.
Hear, hear!
Dr. Phinney admits his bias here:
Dr. Phinney claims the data in the studies cited by Dr. Fung in his fasting book were misstated. It would be interesting to have someone experienced in study analysis, e.g., Zoe Harcomb, analyze those studies cited by Dr. Fung.
One major problem Dr. Phinney references is the so-called Refeeding Syndrome:
During refeeding, insulin secretion resumes in response to increased blood sugar, resulting in increased glycogen, fat and protein synthesis. This process requires phosphates, magnesium and potassium which are already depleted and the stores rapidly become used up.
So if you could refeed with a food that does not raise insulin levels much and contained phosphates, magnesium and potassium, like small amounts of fresh fatty meat, refeeding syndrome should be completely avoidable.
Do NOT refeed with plant based foods like “easily digestable” porriage and bread! We know that plants contain antinutrients (poisons) as a defense against predation. People who have been starved may have compromised immune systems that will be hypersensitive to any poisons. OTOH, fresh meat is digested easily and thoroughly in the human small intestine.
Why fasting doesn’t cause muscle loss:
Perfectly understandable 
Do you think we should have French language sub forums? I mean we let the Kiwis have a black channel back channel all for themselves
https://www.ketogenicforums.com/c/community/new-zealand
If enough people would get benefits form a French language sub-forum … We’d be glad to add one.