I ran across this report by Dr Stephen Phinney on the Virta blog. The short story is that he actively opposes IF as a health improvement strategy. I would love to here Richard’s and Dr. Fung’s response to this paper. See the following link to the Virta blog for the details.
https://blog.virtahealth.com/science-of-intermittent-fasting/
I think the Zorn fast of 3-4 days, takes advantage of the optimum days for a fast. I do know that there has been discussion on this though.
K
I do note that’s he 's old, wirey and slim. He practices what he preaches, and has stayed slim. I think that’s telling.
Hey Mike. 
There is a thread on this one: Phinney thinks Long term fasting no benefits
Phinney tends to look at younger, more athletic people without significant metabolic/hormonal problems. For Fung it’s older, heavier people, very often with hormone issues, diabetes, etc.
That said, my opinion is that while Phinney is certainly due massive credit for his past endeavors, he’s somewhat ossified in his thinking and resistant to some of the new information we are getting these days.
For me personally (n=1) if I don’t fast but stick to keto I don’t lose weight or can even put on weight if I don’t watch those macro’s.
Fasting, (IF or ADF) is my key through the door to fat loss.
Many people include time restricted feeding - limiting daily food intake to a restricted time window under the term intermittent fasting. But that is not what this blog article is about, it is focused on fasts of a day or longer in duration.
Personally while I believe there are merits to Phinney’s arguments against fasting I think his concerns are over blown and he is ignoring the many potential benefits. His biggest concern is loss of muscle but that is something that can be monitored, loss of muscle can be slow or negligible, and reversed except for rare pathological cases.
Keto diet will get a person so far, but to win, a person will likely have to do some fasting. OMAD works very good for me.
IF has been the tool for me to lose weight below my set point and keto keeps it off. I have not seen any muscle loss doing a weekly 48 hour fast followed by OMAD or 16/8 on the other days. If I take a week off from fasting I stay the same as I did this week (was I’ll so I skipped my 48.
I can count on 1-2 weekly with fasting now that I’m adapted.
There are many roads that lead to optimal health. What we need to do is determine which is the best one for us. And not presume that what worked for you, will work for everyone.
I am uncomfortable with longer fasts too. Especially as fasting is becoming more and more fashionable.
The vast majority of people do them sensibly and carefully and with at least a basic understanding of what goes on during and after. I use IF and a reduced eating window, sometimes 24 hr fasts, I like it. I have done longer. That’s fine. Long fasts can be great if people know what they are doing.
But every now and then I see a thread or article that makes me flinch. It happens on here and on other forums and sites. Some idiot blasting away full throttle. Extended fasts with a ‘no pain, no gain’ mindset, no awareness of the risks of refeeding syndrome, no understanding of what symptoms should indicate an immediate end to the fast and seeking out medical attention. Extended fasts with low body weight and daily endurance running. Someone ceasing eating and ceasing all meds (insulin, bp, heart, etc.) at the same time with no medical supervision… those kinds of things.
And when/if one of those idiots get dead or hospitalised, it won’t be their idiocy that gets blamed. It will be Fasting.
I saw Phinney say (YouTube vid) that a single death while fasting could set LC and keto back by decades. I agree with him, but the wacky fringe always has its adherents and the voice of reason rarely prevails.
@admins there are two other threads around this issue can they be merged together please?
The one mentioned above by Old Doug and this one:
Don’t worry; it’s easy to do the talk and very hard to the walk. Extended fasting (< a week) takes a tremendous amount of fortitude. Most people do not have the wherewithal to fast themselves to death.
I have seen on other threads people say that about Phinney because it already happened to him. He was poised to ride the LC Atkins wave in the 80s and instead the low fat craze came and he lost out. Since he is in his 60s he does not have decades to wait
I saw that same video a few weeks ago. That seemed to be his over-riding concern… that someone might die when coming out of a fast (faulty refeeding) and set keto back for many years - just as it’s gaining a strong toe-hold.
I don’t know about Phinney, but I think there have been so many people that have been fasting, that perhaps that is no longer an issue. Not that it couldnt happen, but there have already been a great number of successes without problem.
I agree, not only are there many successes BUT even isolated deaths (and there have been some attributed to fasting IIRC) are not enough to derail it. Remember, the Cambridge Diet protein shake debacle was over 50 deaths, and led to Congressional intervention and was in the news for ages with lawsuits etc. Some nutter starves their kidneys to death may stick in some people’s minds but in these days of info-overload, I wouldn’t be particularly worried that too many remember to cause trouble.
Dr. Fung has thousands of patients for whom it works, so I’ll stick with him and Megan.
Me, too!
While I like Phinney, the whole area of fasting is not something I pay much attention to him on. It’s kinda like, why would I let my GP overrule a specialist? Phinney seems to have a pretty good handle on the basics of ketosis. Fung seems to have a very good handle on the specialty of fasting.
People are gonna die. It happens. And it’s gonna be from something. People also do really stupid stuff. I doubt Phinney or Fung or just about anyone else has much control over that short of a clinical setting, which most of us are not a part of.
In no way do I feel even slightly threatened by skipping a meal or two (IF). I don’t feel bad and I don’t believe it’s bad for me. If I did think IF wasn’t right for me, I wouldn’t do it, regardless of the guru touting it or how many letters they had associated with their name.
per @OldDoug Phinney suffered a major setback to his career some 35-40 years ago during a protein shake movement that actually led to a couple of deaths, thereby jeopardizing some fields of research. Couple that with to the best of my knowledge in regards to fasting he is using data that was compiled in the 1930s ( I believe I heard Richard say this following LC Breckenridge. )
I would be gun shy too.
I agree, Brian. I also wonder how much worry about it is really rational. Lots of people die, worldwide, from not eating, but usually it’s because they are chronically badly nourished. It wasn’t that they did a fast of any certain duration.
I’d say that fasting has a place in the prevention of heart disease and strokes, for many people. The application with respect to diabetes is clear. While we don’t know much yet, there may be useful treatments - via autophagy - for some cancers. And while it’s still early on, things are looking pretty good for the prevention of of many cases of Alzheimer’s Disease as well.
Taken as a group, those are some heavy-hitters as far as causes of death. Many millions die of them every year. If fasting results in a tiny improvement, there, it would more than balance out the very few deaths that occur due to fasting.
Phinney really likes good, well done research. I only EF3 days max, because of the research he has. Something about diminishing returns. The fact that he’s old AND skinny makes me think that he’s likely right, or naturally thin. 
K
I really like what Dr Bikman on youtube has to say. He also expresses a concern about coming out of extended, unsupervised fasts by people who are not under competent supervision (or undereducated).
We have all seen people new to keto embarking on long fasts probably without really knowing what they are doing. I think this is where cautious people like Phinney and Bikman think the danger lies. Not in the fasting itself, but in individuals without a good enough grasp of the information about how to re-introduce food into their lives.
And, yes, people do die. But how many might die from ‘improper’ fasting techniques vs those many who die every day from the many complications of diabetes, CVD, etc.
