Strangely, I’ve really begun to enjoy extended fasting. I fast 3-4 days at a time with 2-3 day refeeds; rinse and repeat. One thing that concerns me about this is that although there is a great deal of published research about the effects of a single fast, I don’t believe there has ever been research done on “serial fasting”. Specifically, I’m concerned that a person’s metabolism can adapt over time to fasting. While it may be true that metabolism remains relatively constant during an extended fast the first time, that doesn’t mean on the 20th fast the body is going to react the same way.
Because of this concern, I’m going to get my RMR measured so that I know what shape my metabolism is in currently. I’m on my 8th three day fast since December, and I’d like to know what it’s doing to me. If my RMR is in line with the predicted RMR using the Harris-Benedict or Katch McCardle equations, then all is well. If it’s significantly lower, well then I’m going to have to make some adjustments. I’m planning on having it done quarterly until I hit my maintenance weight. Reading about those “Biggest Loser” contestants in Fung’s book was eye opening. Those poor folks wrecked their metabolisms for life, and all of them regained massive amounts of weight. I don’t want to be that guy!
RMR testing is actually pretty cheap. You can get it done out of pocket for about $100. I live in a very small city and there were actually 3 places to get it done within 10 miles of my house.
So here are a couple of questions for the community:
Is anyone aware of any published research about people who have done an extended fasting (a 3 days or more), on more than 1 occasion?
Has anyone out there had their RMR tested after doing a fasting regimen for a few months? What was your fasting regimen, how did the RMR come back?
Is anyone aware of research regarding “rebuilding” metabolisms? Surely it’s not unusual in this day and age of yo-yo dieting for people to have a messed up metabolism and hunger hormones? Are there treatments/strategies that we could do to be protective of our metabolisms?
That’s the problem with what we’re doing: there’s no evidence one way or the other.
I personally stopped IF or longer term fasting for a while, as I was getting freezing when fasting even 12 hours. My hands would get so cold I couldn’t touch myself. I took a while off AND also radically increased my iodine intake. I feel better now, and am back to fasting (attempting 36 hours x 2 next week), but I don’t know whether one of those or both worked to reduce the freezing feeling I was getting. And therefore I don’t know whether that was RMR decreasing, or what.
This is a comparison of CR (calorie restriction) versus ADF (alternate day fasting):
Another factor that may have contributed to the more favorable changes in body composition in ADF is RMR. When adjusted for FM and FFM, RMR decreased significantly in CR but not in ADF over the 8-week intervention with a trend (p =0.076) for a between-group difference. Other studies have found a decrease in RMR greater than expected due to changes in body composition alone with weight loss induced by CR [31, 32] consistent with what was observed in the CR group over the 8-week intervention. The apparent impact of ADF on preserving RMR during weight loss could have clinical significance in preventing weight regain after weight loss and should be explored in larger studies.
Yeah, I’m familiar with that one. It’s one of the few ADF studies where the “Fasting” day wasn’t 500kcal of carbs and crap. They should call 75% of the published “ADF” studies "Alternate Day Calorie Restriction) so people don’t get confused.
At any rate 3-5 days is whole lot different than 1 day! You may be right that there is no published study but I’m hopeful.
I’d settle for a handful or so n=1 accounts. There are thousands of us doing extended fasting for weight loss serial basis. An RMR is only $75-$100 in many places. Surely some of us have gotten an RMR? I see dozens of DEXA scan posts, but DEXA costs twice as much, and most facilities that do DEXA also have RMR. Maybe folks aren’t posting RMR because they don’t think anybody would be interested?
Personally, I think if you’re fasting 100 days out of the year, it’s not a bad idea to what it’s doing to your metabolism. Heck, I fast 18 (non-consecutive) days last month. I’m hoping to crowd source some data so we can all see what the patterns emerge.
One of the problems I foresee with RMR is interpreting the results. Assume you go from 250 pounds to 200 pounds. Your RMR should drop by 50/250*100 = 20%. That is, if RMR is linear (meaning that every 1% decrease in body weight = 1% decrease in RMR), but I have no idea whether that’s true. You should lose muscle mass, as you no longer need to carry 250 pounds around. But maybe you’re lifting weights and this results in a net muscle mass gain. Then, what should RMR be?
Another musing I had is that at some point, fasting will look like low calorie. In other words, if you keep fasting and eating, but don’t eat “enough” (whatever that is), your body (logically) should reduce energy output beyond what a “normal” RMR should be at your current weight. This, I think, is the crux of your question: when and why does this happen? But I’m not sure anyone knows.
When I see people trying to fast 5 days and eating one, then fasting 5 days and eating one, and repeating, I think to myself that is a bad idea. But I have no evidence it actually is bad.
Great question. I assumed at first that only a hospital would be able to do it. Then I realized that there are lots of “clinics” that do “supervised weight loss”. They have RMR machines. There are 3 places around my little city in upstate NY that do it. The supervised weight loss clinic near me quoted me $150. In most cities you can get done for $50-$100. The Bariatrics Ward of the hospital quoted me $900 (in fairness, the also charge $50 for an aspirin). It only takes 10 minutes.
Another good way to do it is to google “DEXA” and your the name of the nearest city. Most places that offer DEXA scans to the public offer RMR and VO2 max testing as well. There are a lot of them. Dexafit is a big chain of such centers.
Good on you for stopping when you got the signals. Lots of people try to power through only to find their “fasting” muscle has been broken. You should get your RMR checked if there’s one around and the budget supports it. The only studies we have of long term fasting are folks who did it once. I’ve got a feeling that the metabolism is fickle and clever beast, and adapt to anything we throw at it. It may take 4 days for the metabolism to slow in a virgin faster, but for folks like us it could be 24hrs because the body has adapted and knows what’s coming. Truth is, nobody knows!
Here is some vintage Russian (case-studies) research:
Concluding Thoughts (Cristi Vlad): From these reports we also find out of patients with poor response to therapeutic fasting. Once again, we are all different. What works for me may not work for you. Complications may appear predominantly during the acidosis phase. Complications such as nausea and dizziness may be counteracted by drinking alkaline water (rich in bicarbonate). If nausea persists for more than 3 days, fasting should be interrupted.
Complications may also appear during the realimentation phase. They are mostly due to excessive food intake. We know of historical therapeutic fasting reports (found in the medical literature) when patients died of complications in the realimentation phase* (see more here).
There are cases when cycles of fasting may have to be implemented – such as with severe pathologic conditions. A second cure, as per Dr. Nikolayev, may be even more efficient and it may require fewer days of fasting because the body is now familiar with this intervention. He suggests a window of at least 6 months between these cures. …More
Thanks for those links. Interesting stuff! I’d love to read Dr. Likonayev’s book to learn more details like the tables of patient data and so forth but my Romanian is admittedly a bit rusty. It’s fascinating that a Russian doctor treated upwards of 10,000 people with 30 day water fasts for the treatment of disease. I’d never ever heard of the guy but I sure would love to see his data.
The fasting that the quotes/links refer to are 30 day water fasts for disease rather obesity, and the famous 382 day water fast in Scotland. Those are a bit more extreme than most of us contemplate undertaking.
first I am not sure I believe the myth of permanent metabolism damage. I am aware of the biggest loser report but I still think there is something wrong in the final conclusion.
I think if your body was not able to figure out your diet rhythm and relate it to circadian cycle, it will not be able to take decision to lower metabolism.
Also a relative reduction in energy expenditure is logical and normal. An unloaded truck will consume less gas than when it is loaded. bigger version of my body will require more energy to maintain and operate.
I believethere is no risk in doing what you are doing. I am doing three day EF but monthly not weekly.
I believe that all metabolic slow down are reversible including the biggest loser.
in the case of the biggest loser, the severity of the program is not realistic and can not be related to real life that is why it may takes them longer to reverse their metabolic slow down.
@ctviggen and @Don_Q … I have been a serial water faster since August 2018 and have lost 40+ pounds and feel quite well overall. I water fast 3-4 days every week. ADF and I don’t do very well.
I too have periods of cold/chills around days 2 and 3 of 4-day fasts. If severe and it persists I check my blood glucose level. If too low — in the 50s — I break the fast. If it’s OK I just move a little, take a hot shower or cover up and it passes. Most of the time I notice that there is a glass of ice water on the table next to me. Duh!
I’ve been concerned about harming my metabolism but I feel I had crapped on it already with decades of high carb eating. I understand all the RMR concepts and battle low RMR by eating really well during 3-day re-feeding period. My body surely won’t think it’s starving.
I also have avoided heavy lifting because I have bradycardia and had a heart attack 15 years ago. At age 68 I can’t tolerate too much anerobic output. I opt for long, fairly vigorous walks 3-4 times a week. (My dog loves it.)
I use the VA for some of my health care and can get DEXA scans free but I have to drive 75 miles into downtown New Orleans and that is to be avoided. I do intend to have at least once this year. But I have no baseline.
I wish I could add clinical and scientific data for you. I can only give my anecdotal observations but the preponderance of everyone’s similar findings seem to indicate that serial fasting is beneficial IF done in a reasonable and attentive manner. Eat well in between fasts and monitor yourself while fasting — don’t be afraid to “cave” if not feeling well.
I don’t think Keto alone would heal my metabolic derangement (not T2) alone. I am one who needs some fasting to lose weight and heal.
Totally fair point. “Permanent” is definitely too strong of word. And to your point, most of the media coverage was a muddled mess because they really didn’t understand what they were talking about. The conclusions the media drew were sensationalized and not valid. That doesn’t detract from the study itself however.
We can say for sure that after 6 years, the Biggest Loser contestants had a average metabolic adaptation of a 500kcal/day RMR reduction and that all but one regained the wait (one gall got a gastric bypass). The study was reasonably high quality, as it was undertaken directly by the National Institute of Health, and the RMR gear was a top of the line Parvo Metabolic Cart. Below is the link to the full journal article and the relevant table from the study.
Dr. Fung mentions a study (somewhere in his voluminous compendium of blog posts) where the average metabolic gain was 13% after 4 days of fasting. Increased secretion of norepinephrin and lowered insulin could account for that. He also says that alternate day fasting, studied over 22 days, showed the basal metabolism being maintained, even while steadily losing weight. Cool.
I’m going to test myself, but it really has to wait a couple years until I’m retired and can be home all the time. $3000 or $4000 is what I think it takes to get a tester, so not cheap, and there are some consumables that have to be replaced over time. I want to do it at least once a day, so the prices at external testing places will add up too fast for me.
We know that calorie restriction leads to metabolic slowdown, eventually. Certainly by 5 or 6 months, as with the ‘Biggest Losers’ and the Minnesota Starvation Experiment. I don’t think a few days or even a week does, so somewhere between that and 5 months is where I put the probable point at this time.
As for outright fasting, we’re woefully short on information, and since it doesn’t involve people taking drugs or eating processed food, there’s not much available money or interest for it among the usual suspects, as far as sponsors.
Fung says that for maintaining/fixing lowered metabolisms, the key is to not shortchange our bodies on energy. If fat stores cannot be accessed, due to high insulin levels, then if we restrict calories from food, our body will deal with it by slowing things down. To be protective of our metabolisms, then, I’d say don’t restrict calories - and/or make every effort to keep insulin low (and the keto diet and fasting both work directly toward that).
“Rebuilding” a slowed metabolism is probably harder. Most of the Biggest Losers had slower metabolisms, even after 6 years, as you read - definitely gives one pause. Fung says that opening up the door to our stored fat means the body will sense the increased supply and increase the metabolism, but he doesn’t give any actual studies behind this, that I’ve seen.
Anecdotally - I’ve got 20-25 fasts of 3 days or more in. On the very first one, I felt a little cold on the 3rd day of 4.5 - my feet were cool one night. Other than that, nothing, and I’ve even felt some flushing/persistent hot flash-type feeling stuff where I think I’m revved-up.
Yup! It was exactly these points you listd that got me to try this crazy method of weight loss and insulin overhauling! But those studies were of people fasting for the first time. What happens after the 50th time? Metabolisms are clever little beasts; I think adaptations will occur. Nobody really knows.
I’ve actually been shopping for one all week. I want to take my RMR daily for the next 80lbs to see what sort of craziness is occuring. I’m looking at the Korr Medicheck. You can pick one up new for $3,330. Be very careful about the used indirect calorimeters on Ebay. Korr is very solid brand, but the O2 sensors need to be replaced every 18-24 months. For the original owner it’s only $335, but if you buy it used, they charge you $1,095 to replace the O2 sensor. Most of the units on Ebay have an expired O2 sensor. When that’s the case, you can’t even tell if it’s damaged. You could spend $1,500 and get a phone call from Korr that it can’t be re-calibrated. Now you’re short $1,500 and you own a paperweight. Be careful too about the consumables. Korr’s uses disposable Meta-breather hoses that cost $10.00 each. You can buy a reusable Y valve made by a medical device supplier named Hans Rudolph, but that ain’t cheap either.
I know a guy on another forum that just bought a new Korr Metacheck. He’s on vaca next week, but he’s starting his daily testing the week after that. He’s already lost 90lbs if I recall. Interestingly, he’s reporting exactly the same symptoms that @GentleBen did. He says that he never got cold in the past year of cycle fasting, but now he does. It made him nervous. He’s not sure whether it’s a metabolic adaptation, and if so, what precisely is happening. It may just be that he’s skinnier. He’s gonna find out.
In your case @OldDoug you can get an RMR done for $100 or so if you just want to know where you’re currently at. If you do, I know I’d be super curious. I’ve only done 8 3-day fasts so far so you’re way ahead of me.
My understanding is that declining metabolism begins pretty quickly. It starts happening in the first few weeks of calorie restriction for most people and continues a downward slope until calories increase. There are a lot of variables obviously. Individual people vary, and the rate of decline can be influenced the magnitude of the restriction. Nobody has ever published data on what happens to the RMR’s of people who cycle fast. Hence my interest trying to find folks here that do keto, cycle fast, and have had an RMR.
Agreed 100%. I eat to satiety on feast days. Sometimes that turns out to be a crazy number of calories. I lift weights prior to breaking my 84hr fasts, and I find on the next day I get very,very hungry. Sometimes I go North of 4000kcal that day which is crazy to me. I dropped two pant sizes last month though, so I KCKO.
You hit the nail on the head. That’s why I’m interested in buying an indirect calorimeter to measure my RMR daily. I want to watch it like a hawk and see what’s happening. I don’t mean to seem alarmist though, I think it’s entirely possible that cycle fasters who feast hard may in fact be increasing their RMR. If so, that’s a big,big deal.
I currently know of 3 people who have cycle fasted and had an RMR done. I’d like to find at least a dozen more so maybe we can figure out what happens. Like you said, nobody else has any idea!
Great information, Nick. I inquired at Korr about their ReeVue as well as the Medicheck. A representative called me back; I missed the call. It will be fascinating to track exactly what is happening.
As for mutiple fasts over the long term, it’s still really hit-or-miss for me. Fasting has gotten easier overall, the more I do it, but still never know what a given fast will be like. My last three were: 3 days - didn’t feel great, ended sooner than I wanted, then another 3 days, same result, then a 5.5 day one where I felt great and had a new thing for me - during the third day, while in bed, got a really warm ‘glowing’ feeling from the shoulders to the top of the head. Not like being hot/sweaty or uncomfortable at all - man, this was great, like a partial religious experience or something.
One generalization I’d make is that I haven’t felt colder or hotter on the whole over all the fasts - 22 months.
