11 ms·

Fasting lowers blood pressure by reshaping the gut microbiota

128 points by porterde 5y ago

omosubi 5y ago
I just did a 40 hour fast to see if i could do it and it was a lot easier than i thought it would be. I'm trying to build up to a week long. We'll see how it goes. It's a shame that fasting has been eliminated from the culture, but i guess that's what happens to things you can't make money on.
- Engineering-MD 5y ago
  Just a word of caution, after 7-10 days of fasting, you can get refeeding syndrome. This can be pretty unpleasant and dangerous, and is best avoided.
  - alecst 5y ago
    Hey man, sorry to call you out. I want you to find where you heard that, and maybe post it here so that we can review. I have fasted many times for that length, and I happen to already be thin. Never even got close to refeeding syndrome. I've read a variety of books on the subject. I've spent some time on PubMed. I don't know everything about fasting -- absolutely not -- but I know enough to say that you might be misremembering the time it takes to get refeeding syndrome. I personally believe the number is closer to 30 or 40 days. We are talking Christ-level fasters, hunger strikers, performance artists, or concentration camp victims. I downvoted your comment because I consider it to be spreading misinformation, and because your tone indicates that you have expertise or experience on the matter.
    - float4 5y ago
      You can definitely get refeeding syndrome after 7-10 days of fasting. It depends on your your fat reserves, health, and lifestyle. Say I'm 192cm and 69kg. My BMI is 18.7, which is definitely low, but perfectly healthy. I have an active lifestyle and burn 3500kcal per day. If I fast for 7 days without changing lifestyle, I lose roughly 7*3500/7700=3.2kg of bodyweight. By that point my BMI is 17.9. According to this paper[0] with 632 citations, anyone with a BMI <18.5 who's not eaten for more than 5 days is at high risk of refeeding syndrome. If you think the numbers are fictional: those are my numbers from ~5 years ago. [0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2440847/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2440847/
      - alecst 5y ago
        Cool, if it’s that clear cut I’m sure you can find a few cases to make your point. It is rare that eating after fasting causes critical illness. Just check online. People do this stuff all the time.
        float4 5y ago
        I wasn't making "my point". I just knew your comment about 30-40 days and the random mentioning of concentration camp victims was absurd, and it clearly is according to official clinical guidelines. So no, I won't "just check online".
        alecst 5y ago
        > Historically, some of the earliest reports of the refeeding syndrome occurred in starved patients in wartime such as Japanese prisoners and victims of the Leningrad or Netherlands famines. In general, those individuals with marasmus or kwashiorkor are at risk for the refeeding syndrome, particularly if there is greater than 10% weight loss over a couple of months. Patients are at risk if they have not been fed for 7 to 10 d, with evidence of stress and depletion. However, more specifically, this syndrome also has been described after prolonged fasting, massive weight loss in obese patients including after duodenal-switch operations, chronic alcoholism, prolonged intravenous fluid repletion, and anorexia nervosa. Anorexia nervosa is one of the more common modern clinical presentations of the refeeding syndrome, as are oncology patients undergoing chemotherapy, the refeeding of malnourished elderly individuals, and certain postoperative patients. https://www.hopkinsmedicine.org/gim/_pdf/consult/refeeding_syndrome.pdf https://www.hopkinsmedicine.org/gim/_pdf/consult/refeeding_s...
- thebean11 5y ago
  When you say a week of fast, what are you consuming? Surely you need something beyond water for such a long fast right?
  - dageshi 5y ago
    Average healthy but overweight (yes I know this might be a contradiction in terms) person can fast that long pretty easily without eating anything. That's why the body stored the fat in the first place...
  - sneak 5y ago
    Water, electrolytes, and a multivitamin should be more than sufficient.
  - ijidak 5y ago
    The body stores fat for the exact purpose of surviving limited access to food. Most Americans could go weeks without eating, and they'd be mostly fine. Sudden refeeding is an issue, of course, because of electrolyte balance. But we have a misunderstanding of how long the body can go without food, by design. What we mainly need is water during periods without food. After about 3 days without food, the body stops telling you your hungry and switches to fat metabolism.
  - coldtea 5y ago
    You don't need anything "more than water", but you do need some electrolytes thrown in for correct hearth operation.
  - gwd 5y ago
    > Surely you need something beyond water for such a long fast right? You need electrolytes for sure; but unless you've recently been prepping for a body-building competition, you don't need any calories for quite a bit longer than that. I did a week-long fast for religious purposes many years ago, before the whole IF health craze was a thing. All I had was water, and occasionally some salt. I still had plenty of fat at the end of it, and I wasn't particularly heavy before. According to the book I read at the time (again, focusing on fasting for religious purposes), it's only after 3-4 weeks that a typical person experiences a more urgent type of hunger pang, which is the indicator that your body is starting to cannibalize critical infrastructure (and that it's probably time to stop fasting if you don't want to damage your health). People who are actually overweight presumably have enough calories to last for months. Vitamins and minerals are obviously another thing. You're not going to get a nutrient deficiency in a week, but you might well in a month or two. (I am neither a nutritionist nor a doctor.)
- WA 5y ago
  So many gurus right now make a ton of money from the IF (intermittent fasting) craze. You CAN make money off fasting. Sell books and courses. Promise a lot etc.
  - omosubi 5y ago
    You can only make money through courses etc. if the methods aren't already in the culture, and relative to the amount of money you can make selling junk food or health food/vitamins/supplements, the books and courses are a pittance.
- thatguy0900 5y ago
  I did a week long fast. My advice is to be constantly drinking water and sleep as much as you can. Make sure you get enough electrolytes in your water or you will start feeling like you're gonna have a heart attack.
  - Buttons840 5y ago
    How do you get electrolytes in your water?
    - thatguy0900 5y ago
      Mixture of table salt and no salt, the salt free alternative salt you see in grocery stores for potassium chloride
  - zkirill 5y ago
    Forgot about the heart palpitations! That was a fun discovery.
malux85 5y ago
I have been intermittant fasting for a month now and the results are fantastic. The mental clarity alone is worth it, let alone the weight loss and general well being (better sleep, better digestion) I only eat for 4 hours a day, some days 1 meal and grazing, other days 2 meals, but nothing outside those hours except water and tea (with no milk) I feel fantastic, I'm never going back to any other food schedule. The downside was that the first week was incredibly hard, I felt dizzy and had spells of intense anger, but I distanced myself from those I love so as not to accidentally explode at them and just got through it, now after nearly a month, it feels normal and I just feel great. Highly recommend it.
- hnrodey 5y ago
  What are you eating during your four hour feeding window?
  - malux85 5y ago
    Vegetables, steak and fish. I try to avoid carbs
  - matwood 5y ago
    I'm not a no carb person. I've tried no carb and it's just too hard to get the energy I need for my activity levels (I know it can be done, but I also like to do things I can maintain for years). But, I do think about my carbs. Meals consist of cooked veggies (my trinity is peppers, onions, mushrooms) or standard salad. Then some type of protein like fish or chicken. Carbs I'll add if I think I need them that day. Rice or I'll cut up potatoes and sauté or oven roast with rosemary and a little OO. I'll also graze on something like hummus and raw veggies and mix in some pretzels. I avoid sweets though.
    - hnrodey 5y ago
      fwiw I've had better success with low carb diets and energy for workouts when in full blown ketosis (as measured by blood meter). Otherwise, you're kind of in energy purgatory if you simply go low carb.
qwertox 5y ago
When I do sports (riding bike every day for at least one hour in mostly anaerobic mode) after not eating for at least 18 hours or so (which I don't do often), I feel like I've got unlimited resources of energy available.
- amelius 5y ago
  How do you ride bike in anaerobic mode consistently without going dangerously fast? I've been looking for a device that makes pedaling heavier if activated but haven't found it yet.
  - snthd 5y ago
    A parachute?
    - slumdev 5y ago
      The tachycardia experienced by skydivers isn't the same sort of stimulation that exercisers are looking for. But it's an interesting thought.
    - amelius 5y ago
      Hehe, not practical on my daily commute. It also doesn't work with strong tailwinds.
  - dillondoyle 5y ago
    stationary bike. but keeping a top % hr for an hour straight is very impressive if true.
  - fahadkhan 5y ago
    A dynamo connected to a resistance will do. An old bike had a dynamo connected to a rechargeable light, the bike felt heavier the more the battery depleted. Alternatively get a Turbo trainer or rollers with resistance for stationary training. Lots of people love it but it's not for me, though rollers aren't bad but the it gets very hot even outdoors with a fan.
walshemj 5y ago
Interesting after I had been on antibiotics continuously for an extended period - the corelectoral surgeon prescribed a course of symprove probiotic. Which does seem to make me feel a lot beter il have to experiment with fasting as well.
mavci 5y ago
Did you know that fasting for one month a year is obligatory in Islam? “O you who have believed, decreed upon you is fasting as it was decreed upon those before you that you may become righteous. Fast a prescribed number of days. But whoever of you is ill or on a journey, then let them fast an equal number of days after Ramaḍân. For those who can only fast with extreme difficulty, compensation can be made by feeding a needy person for every day not fasted. But whoever volunteers to give more, it is better for them. And to fast is better for you, if only you knew.“ - Surah Al-Baqarah 183-184
- deleted 5y ago
  [deleted]
- roveo 5y ago
  As far as I know, during Ramadan you're only allowed to eat and drink when it's dark, which is more like a pretty extreme version of intermittent fasting (depending on daylight duration).
  - dillondoyle 5y ago
    And the Iftar tradition basically to break fast with a giant meal each sun downn. Makes it seem even more extreme up and down.
  - mavci 5y ago
    yes depending on your daylight, approximately, it takes between 13 and 18 hours. I am fasting one month a year, more than 10 years, and I can’t call extreme, it’s more like need
  - deleted 5y ago
    [deleted]
- elliekelly 5y ago
  I wonder whether anyone has studied the weight (or even gut bacteria) of observant muslims compared to the population at large.
shoto_io 5y ago
I regularly do IF and have seen great results for my weight and blood pressure. Just a word of caution about this study: it’s still only an animal model (rats). Should be added to the title for clarity.
foobiekr 5y ago
The gut biome must be at least strongly influenced by the environment you create - change should be assumed as soon as you change that environment. But does the change mean anything? I think this is going to turn out to be an incomprehensible problem that we will never really get a handle on due to the time it would take to even begin to understand things. We just aren’t able to run those experiments and this is the general domain where science for us fails and degenerates to just-so stories and observational correlations “studies.” To illustrate… Last year I did 5 months of OMAD to lose weight. I’d gained a bunch in the first few months of lockdown. It wasn’t hard but it wasn’t easy especially because my wife, who is effortlessly slender and eats a ton, needs to eat a big breakfast every day. I often wonder if a gut biome transplant from her would give me that - I’d love to see someone actually do that experiment. But not on me. Her and her brother can literally eat bags of iced mothers cookies per week and stay slender - her GP says she needs to gain weight. It just isn’t going to happen. It took me awhile to understand what’s going on but my observation is they get really warm and fidgety for the hours after overeating and just burn it off sitting there. Her whole family is pretty lazy, they don’t exercise recreationally. They aren’t running it off or whatever. Whereas my chronically overweight family lives ends up with moderately high boood pressure, they also all live long lives mostly free of debilitating illness until the end. Her family, on the other hand, has all manner of terrible issues once they hit their 70s… Obviously this could just be “genetics” but whose? Their nuclear genetics or their inhabitants? And do the long terms come out of that? I honestly don’t think we will ever know without experiments. And given things like the above I wonder if they can be even done, even if you decided to ignore the potential long term…
- beckingz 5y ago
  OMAD = One Meal A Day
- winrid 5y ago
  Makes me wonder if having a higher metabolism somehow "wears out your body faster". My wife and I are the opposite. I can eat a cheeseburger every night and stay slender + low chloresterol etc. I do OMAD twice a week, which probably helps a little. It doesn't feel natural to always say three meals a day.
snthd 5y ago
https://doi.org/10.1161/CIRCRESAHA.120.318155 https://doi.org/10.1161/CIRCRESAHA.120.318155
inglor_cz 5y ago
N == 1 here. I had a huge drop in blood pressure once I started fasting daily. Even though I lost only a modest amount of weight (approx. 10 pounds; I was never obese, only slightly overweight with BMI cca 27), my blood pressure plummetted from 150/95 with medication to some 115/75 without medication within a month. This holds even when I no longer fast daily, only a few times a week. Additional Concor, taken against post-Covid arrhythmias, reduced my BP to some 105/70 when relaxed. Going any lower would actually mean a risk of fainting. This seems to be consistent with the theory of gut microbiota being reshaped. I can also tolerate milk slightly better than before; my tolerance still has limits, but I won't get a rash after a single cappuccino, which I most definitely used to before.
- pokot0 5y ago
  Do you mind sharing your daily fasting routine. I only tried intermittently and always wanted to give it a more serious try and I have to start somewhere.
  - inglor_cz 5y ago
    My sweet spot seems to be 18/6. I prefer to go without breakfast and have a lunch and a dinner 6 hours apart, because I hate to sleep with an empty stomach. I drink unsweetened coffee and tea (0 calories and may act as appetite suppressant). I generally limit sugar in my food, though not to zero. On my non-fasting days, I have a breakfast, but I try to have no more than 3 meals a day. No snacking. I decide whether to fast or not by the state of my hunger in the morning. If I am ravenous, I have a breakfast and a non-fasting day. If I feel only slightly empty, I go without breakfast to a total length of 17-19 hours of fasting. I am now experimenting with continuous glucose meter to find out what meals send my glucose too high. This, again, seems to be individual. Rice and potatoes seem to act really crazy. Interestingly, pizza not so much.
    - 1_player 5y ago
      18/6 has never done anything to my BP, I've been doing it for 10 years. I suspect the biggest impact was trying to lose weight and changing your diet. In my case changing my diet has noticeable and immediate effect to any physiological metric than any other "trick".
rozab 5y ago
Does anyone have any fasting advice from a reputable health authority? For some reason the NHS doesn't really have any online, even though a sizeable proportion of the population observe Ramadan. They usually have good, well-cited articles on this kind of thing.
- reedjosh 5y ago
  Governmental health bodies are very behind on this topic. They used to even claim fasting was terribly unhealthy.
- tdaltonc 5y ago
  What sort of advice are you looking for? I wrote this, most of the links are to primary research on fasting. https://usetemper.com/learn/metabolic-fitness-no-bigger-opportunity/ https://usetemper.com/learn/metabolic-fitness-no-bigger-oppo... Most of the primary research isn't really focused on generating "advice." If I had to pick the protocol with the best direct evidence, I'd pick "early time restricted feeding" (eTRF). https://pubmed.ncbi.nlm.nih.gov/29754952/ https://pubmed.ncbi.nlm.nih.gov/29754952/ That's what Brian Johnson practices. It's not a fasting protocol I would actually recommend to most people because it's pretty inconvenient, but it's been directly studied as an intervention.
frereubu 5y ago
This study is in rats, and if I'm reading the article correctly it also involves a population of rats that are bred to be predisposed to hypertension. So although it sounds like there are some interesting anecdata stories in the comments, this is very far from being generalisable to human populations. Seems like it would be a pretty easy study to do in humans though, to the point where I wonder if it hasn't been done already, even if not specifically focused on gut bacteria.
- tdaltonc 5y ago
  Intermittent fasting has previously been shown (in humans!) to lower blood pressure. https://pubmed.ncbi.nlm.nih.gov/29754952/ https://pubmed.ncbi.nlm.nih.gov/29754952/ https://pubmed.ncbi.nlm.nih.gov/28202779/ https://pubmed.ncbi.nlm.nih.gov/28202779/ https://pubmed.ncbi.nlm.nih.gov/19793855/ https://pubmed.ncbi.nlm.nih.gov/19793855/ Also improve insulin sensitivity, reduce glucose and/or insulin levels, improve lipid profiles, and reduce markers of inflammation and oxidative stress. https://pubmed.ncbi.nlm.nih.gov/23408502/ https://pubmed.ncbi.nlm.nih.gov/23408502/ https://pubmed.ncbi.nlm.nih.gov/27833048/ https://pubmed.ncbi.nlm.nih.gov/27833048/ https://pubmed.ncbi.nlm.nih.gov/27569118/ https://pubmed.ncbi.nlm.nih.gov/27569118/ https://pubmed.ncbi.nlm.nih.gov/23497604/ https://pubmed.ncbi.nlm.nih.gov/23497604/ https://pubmed.ncbi.nlm.nih.gov/16051710/ https://pubmed.ncbi.nlm.nih.gov/16051710/ https://pubmed.ncbi.nlm.nih.gov/23591120/ https://pubmed.ncbi.nlm.nih.gov/23591120/ https://pubmed.ncbi.nlm.nih.gov/20921964/ https://pubmed.ncbi.nlm.nih.gov/20921964/ https://pubmed.ncbi.nlm.nih.gov/27233359/ https://pubmed.ncbi.nlm.nih.gov/27233359/ https://pubmed.ncbi.nlm.nih.gov/15833943/ https://pubmed.ncbi.nlm.nih.gov/15833943/ https://pubmed.ncbi.nlm.nih.gov/15640462/ https://pubmed.ncbi.nlm.nih.gov/15640462/ https://pubmed.ncbi.nlm.nih.gov/28035343/ https://pubmed.ncbi.nlm.nih.gov/28035343/ https://pubmed.ncbi.nlm.nih.gov/25251676/ https://pubmed.ncbi.nlm.nih.gov/25251676/ https://pubmed.ncbi.nlm.nih.gov/17291990/ https://pubmed.ncbi.nlm.nih.gov/17291990/ https://pubmed.ncbi.nlm.nih.gov/22889512/ https://pubmed.ncbi.nlm.nih.gov/22889512/ https://pubmed.ncbi.nlm.nih.gov/29258678/ https://pubmed.ncbi.nlm.nih.gov/29258678/ https://pubmed.ncbi.nlm.nih.gov/25546413/ https://pubmed.ncbi.nlm.nih.gov/25546413/
  - frereubu 5y ago
    Thanks for the (copious!) links.
vericiab 5y ago
I don't tend to experience hunger and, as a result, interrupting my activities to eat multiple times per day can feel like a bit of an inconvenience. So I've frequently fasted daily since before "intermittent fasting" entered the common lexicon. It's not really intentional though, I will quite literally forget to eat or otherwise just don't make it a priority. In my experience, I'm not sure it's quite the panacea it's sometimes made out to be. Perhaps there are psychological benefits to intentionally fasting that I'm missing out on. In any case, quite often when I'm wondering why I feel like shit I end up realizing something like I haven't eaten in 24 hours or in the last 48 hours I've eaten less than 1000 calories. Oops. I'm trying to be better about regularly eating 2 meals per day because I really do feel better if I've been eating consistently. I'm not sure it's doing my blood pressure any favors either. Despite regular fasting and having a BMI of 18.1 (technically slightly underweight, as the lower bound of a "healthy" BMI is 18.5), my blood pressure is usually around 140/95. But who knows, maybe it would be higher without the fasting.
- dlp211 5y ago
  Intermittent fasting is not the same thing as malnutrition or fasting in excess. Continually not eating for 24-48 hours and/or depriving yourself of necessary calories isn't good for anyone.
zkirill 5y ago
Fasting was one of the most memorable and shaping experiences of my life. I fasted for three days (72 hours of nothing but water) and observed so many interesting and fascinating things happening to my body each day: skin flare ups and subsequent clearings, changes in mouth and gut odour, periods of brain fog and brain clarity, cravings followed by complete loss of feeling of hunger. Every passing day had different effects. The most memorable was an astronomical improvement in my olefactory senses. By day two I was able to pick out the smell of individual ingredients in any dish being prepared in my vicinity. By day three, I lost the majority of my muscle mass. The one and only time I ever did this was when I was young and in extremely good health (daily intense exercise, excellent diet, no health conditions). Slightly worried about doing it again today. Also, quite concerned having since learned that brain mass is the first stored energy source your body will go after during what is effectively starvation. Perhaps someone more knowledge on here can comment on how true that is.
- xedrac 5y ago
  I highly doubt you lost the majority of your muscle mass, unless you had very little fat on your body. More likely is you depleted all glycogen stores in your muscles which is mostly water, making your muscles deflate significantly.
  - zkirill 5y ago
    Maybe you're right. It was a long time ago. The only points of data that I have is that I had a "college athlete" level of fat around my heart as per my sonogram and it took me months of work to rebuild my muscle mass.
    - ekabod 5y ago
      You don't seem to know what a muscle is.

128 points by porterde 5y ago

I just did a 40 hour fast to see if i could do it and it was a lot easier than i thought it would be. I'm trying to build up to a week long. We'll see how it goes. It's a shame that fasting has been eliminated from the culture, but i guess that's what happens to things you can't make money on.

Engineering-MD 5y ago
Just a word of caution, after 7-10 days of fasting, you can get refeeding syndrome. This can be pretty unpleasant and dangerous, and is best avoided.
- alecst 5y ago
  Hey man, sorry to call you out. I want you to find where you heard that, and maybe post it here so that we can review. I have fasted many times for that length, and I happen to already be thin. Never even got close to refeeding syndrome. I've read a variety of books on the subject. I've spent some time on PubMed. I don't know everything about fasting -- absolutely not -- but I know enough to say that you might be misremembering the time it takes to get refeeding syndrome. I personally believe the number is closer to 30 or 40 days. We are talking Christ-level fasters, hunger strikers, performance artists, or concentration camp victims. I downvoted your comment because I consider it to be spreading misinformation, and because your tone indicates that you have expertise or experience on the matter.
  - float4 5y ago
    You can definitely get refeeding syndrome after 7-10 days of fasting. It depends on your your fat reserves, health, and lifestyle. Say I'm 192cm and 69kg. My BMI is 18.7, which is definitely low, but perfectly healthy. I have an active lifestyle and burn 3500kcal per day. If I fast for 7 days without changing lifestyle, I lose roughly 7*3500/7700=3.2kg of bodyweight. By that point my BMI is 17.9. According to this paper[0] with 632 citations, anyone with a BMI <18.5 who's not eaten for more than 5 days is at high risk of refeeding syndrome. If you think the numbers are fictional: those are my numbers from ~5 years ago. [0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2440847/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2440847/
    - alecst 5y ago
      Cool, if it’s that clear cut I’m sure you can find a few cases to make your point. It is rare that eating after fasting causes critical illness. Just check online. People do this stuff all the time.
      - float4 5y ago
        I wasn't making "my point". I just knew your comment about 30-40 days and the random mentioning of concentration camp victims was absurd, and it clearly is according to official clinical guidelines. So no, I won't "just check online".
        alecst 5y ago
        > Historically, some of the earliest reports of the refeeding syndrome occurred in starved patients in wartime such as Japanese prisoners and victims of the Leningrad or Netherlands famines. In general, those individuals with marasmus or kwashiorkor are at risk for the refeeding syndrome, particularly if there is greater than 10% weight loss over a couple of months. Patients are at risk if they have not been fed for 7 to 10 d, with evidence of stress and depletion. However, more specifically, this syndrome also has been described after prolonged fasting, massive weight loss in obese patients including after duodenal-switch operations, chronic alcoholism, prolonged intravenous fluid repletion, and anorexia nervosa. Anorexia nervosa is one of the more common modern clinical presentations of the refeeding syndrome, as are oncology patients undergoing chemotherapy, the refeeding of malnourished elderly individuals, and certain postoperative patients. https://www.hopkinsmedicine.org/gim/_pdf/consult/refeeding_syndrome.pdf https://www.hopkinsmedicine.org/gim/_pdf/consult/refeeding_s...
thebean11 5y ago
When you say a week of fast, what are you consuming? Surely you need something beyond water for such a long fast right?
- dageshi 5y ago
  Average healthy but overweight (yes I know this might be a contradiction in terms) person can fast that long pretty easily without eating anything. That's why the body stored the fat in the first place...
- sneak 5y ago
  Water, electrolytes, and a multivitamin should be more than sufficient.
- ijidak 5y ago
  The body stores fat for the exact purpose of surviving limited access to food. Most Americans could go weeks without eating, and they'd be mostly fine. Sudden refeeding is an issue, of course, because of electrolyte balance. But we have a misunderstanding of how long the body can go without food, by design. What we mainly need is water during periods without food. After about 3 days without food, the body stops telling you your hungry and switches to fat metabolism.
- coldtea 5y ago
  You don't need anything "more than water", but you do need some electrolytes thrown in for correct hearth operation.
- gwd 5y ago
  > Surely you need something beyond water for such a long fast right? You need electrolytes for sure; but unless you've recently been prepping for a body-building competition, you don't need any calories for quite a bit longer than that. I did a week-long fast for religious purposes many years ago, before the whole IF health craze was a thing. All I had was water, and occasionally some salt. I still had plenty of fat at the end of it, and I wasn't particularly heavy before. According to the book I read at the time (again, focusing on fasting for religious purposes), it's only after 3-4 weeks that a typical person experiences a more urgent type of hunger pang, which is the indicator that your body is starting to cannibalize critical infrastructure (and that it's probably time to stop fasting if you don't want to damage your health). People who are actually overweight presumably have enough calories to last for months. Vitamins and minerals are obviously another thing. You're not going to get a nutrient deficiency in a week, but you might well in a month or two. (I am neither a nutritionist nor a doctor.)
WA 5y ago
So many gurus right now make a ton of money from the IF (intermittent fasting) craze. You CAN make money off fasting. Sell books and courses. Promise a lot etc.
- omosubi 5y ago
  You can only make money through courses etc. if the methods aren't already in the culture, and relative to the amount of money you can make selling junk food or health food/vitamins/supplements, the books and courses are a pittance.
thatguy0900 5y ago
I did a week long fast. My advice is to be constantly drinking water and sleep as much as you can. Make sure you get enough electrolytes in your water or you will start feeling like you're gonna have a heart attack.
- Buttons840 5y ago
  How do you get electrolytes in your water?
  - thatguy0900 5y ago
    Mixture of table salt and no salt, the salt free alternative salt you see in grocery stores for potassium chloride
- zkirill 5y ago
  Forgot about the heart palpitations! That was a fun discovery.

malux85 5y ago

I have been intermittant fasting for a month now and the results are fantastic. The mental clarity alone is worth it, let alone the weight loss and general well being (better sleep, better digestion) I only eat for 4 hours a day, some days 1 meal and grazing, other days 2 meals, but nothing outside those hours except water and tea (with no milk) I feel fantastic, I'm never going back to any other food schedule. The downside was that the first week was incredibly hard, I felt dizzy and had spells of intense anger, but I distanced myself from those I love so as not to accidentally explode at them and just got through it, now after nearly a month, it feels normal and I just feel great. Highly recommend it.

hnrodey 5y ago
What are you eating during your four hour feeding window?
- malux85 5y ago
  Vegetables, steak and fish. I try to avoid carbs
- matwood 5y ago
  I'm not a no carb person. I've tried no carb and it's just too hard to get the energy I need for my activity levels (I know it can be done, but I also like to do things I can maintain for years). But, I do think about my carbs. Meals consist of cooked veggies (my trinity is peppers, onions, mushrooms) or standard salad. Then some type of protein like fish or chicken. Carbs I'll add if I think I need them that day. Rice or I'll cut up potatoes and sauté or oven roast with rosemary and a little OO. I'll also graze on something like hummus and raw veggies and mix in some pretzels. I avoid sweets though.
  - hnrodey 5y ago
    fwiw I've had better success with low carb diets and energy for workouts when in full blown ketosis (as measured by blood meter). Otherwise, you're kind of in energy purgatory if you simply go low carb.

qwertox 5y ago

When I do sports (riding bike every day for at least one hour in mostly anaerobic mode) after not eating for at least 18 hours or so (which I don't do often), I feel like I've got unlimited resources of energy available.

amelius 5y ago
How do you ride bike in anaerobic mode consistently without going dangerously fast? I've been looking for a device that makes pedaling heavier if activated but haven't found it yet.
- snthd 5y ago
  A parachute?
  - slumdev 5y ago
    The tachycardia experienced by skydivers isn't the same sort of stimulation that exercisers are looking for. But it's an interesting thought.
  - amelius 5y ago
    Hehe, not practical on my daily commute. It also doesn't work with strong tailwinds.
- dillondoyle 5y ago
  stationary bike. but keeping a top % hr for an hour straight is very impressive if true.
- fahadkhan 5y ago
  A dynamo connected to a resistance will do. An old bike had a dynamo connected to a rechargeable light, the bike felt heavier the more the battery depleted. Alternatively get a Turbo trainer or rollers with resistance for stationary training. Lots of people love it but it's not for me, though rollers aren't bad but the it gets very hot even outdoors with a fan.

walshemj 5y ago

Interesting after I had been on antibiotics continuously for an extended period - the corelectoral surgeon prescribed a course of symprove probiotic. Which does seem to make me feel a lot beter il have to experiment with fasting as well.

mavci 5y ago

Did you know that fasting for one month a year is obligatory in Islam? “O you who have believed, decreed upon you is fasting as it was decreed upon those before you that you may become righteous. Fast a prescribed number of days. But whoever of you is ill or on a journey, then let them fast an equal number of days after Ramaḍân. For those who can only fast with extreme difficulty, compensation can be made by feeding a needy person for every day not fasted. But whoever volunteers to give more, it is better for them. And to fast is better for you, if only you knew.“ - Surah Al-Baqarah 183-184

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roveo 5y ago
As far as I know, during Ramadan you're only allowed to eat and drink when it's dark, which is more like a pretty extreme version of intermittent fasting (depending on daylight duration).
- dillondoyle 5y ago
  And the Iftar tradition basically to break fast with a giant meal each sun downn. Makes it seem even more extreme up and down.
- mavci 5y ago
  yes depending on your daylight, approximately, it takes between 13 and 18 hours. I am fasting one month a year, more than 10 years, and I can’t call extreme, it’s more like need
- deleted 5y ago
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elliekelly 5y ago
I wonder whether anyone has studied the weight (or even gut bacteria) of observant muslims compared to the population at large.

shoto_io 5y ago

I regularly do IF and have seen great results for my weight and blood pressure. Just a word of caution about this study: it’s still only an animal model (rats). Should be added to the title for clarity.

foobiekr 5y ago

The gut biome must be at least strongly influenced by the environment you create - change should be assumed as soon as you change that environment. But does the change mean anything? I think this is going to turn out to be an incomprehensible problem that we will never really get a handle on due to the time it would take to even begin to understand things. We just aren’t able to run those experiments and this is the general domain where science for us fails and degenerates to just-so stories and observational correlations “studies.” To illustrate… Last year I did 5 months of OMAD to lose weight. I’d gained a bunch in the first few months of lockdown. It wasn’t hard but it wasn’t easy especially because my wife, who is effortlessly slender and eats a ton, needs to eat a big breakfast every day. I often wonder if a gut biome transplant from her would give me that - I’d love to see someone actually do that experiment. But not on me. Her and her brother can literally eat bags of iced mothers cookies per week and stay slender - her GP says she needs to gain weight. It just isn’t going to happen. It took me awhile to understand what’s going on but my observation is they get really warm and fidgety for the hours after overeating and just burn it off sitting there. Her whole family is pretty lazy, they don’t exercise recreationally. They aren’t running it off or whatever. Whereas my chronically overweight family lives ends up with moderately high boood pressure, they also all live long lives mostly free of debilitating illness until the end. Her family, on the other hand, has all manner of terrible issues once they hit their 70s… Obviously this could just be “genetics” but whose? Their nuclear genetics or their inhabitants? And do the long terms come out of that? I honestly don’t think we will ever know without experiments. And given things like the above I wonder if they can be even done, even if you decided to ignore the potential long term…

beckingz 5y ago
OMAD = One Meal A Day
winrid 5y ago
Makes me wonder if having a higher metabolism somehow "wears out your body faster". My wife and I are the opposite. I can eat a cheeseburger every night and stay slender + low chloresterol etc. I do OMAD twice a week, which probably helps a little. It doesn't feel natural to always say three meals a day.

snthd 5y ago

https://doi.org/10.1161/CIRCRESAHA.120.318155 https://doi.org/10.1161/CIRCRESAHA.120.318155

inglor_cz 5y ago

N == 1 here. I had a huge drop in blood pressure once I started fasting daily. Even though I lost only a modest amount of weight (approx. 10 pounds; I was never obese, only slightly overweight with BMI cca 27), my blood pressure plummetted from 150/95 with medication to some 115/75 without medication within a month. This holds even when I no longer fast daily, only a few times a week. Additional Concor, taken against post-Covid arrhythmias, reduced my BP to some 105/70 when relaxed. Going any lower would actually mean a risk of fainting. This seems to be consistent with the theory of gut microbiota being reshaped. I can also tolerate milk slightly better than before; my tolerance still has limits, but I won't get a rash after a single cappuccino, which I most definitely used to before.

pokot0 5y ago
Do you mind sharing your daily fasting routine. I only tried intermittently and always wanted to give it a more serious try and I have to start somewhere.
- inglor_cz 5y ago
  My sweet spot seems to be 18/6. I prefer to go without breakfast and have a lunch and a dinner 6 hours apart, because I hate to sleep with an empty stomach. I drink unsweetened coffee and tea (0 calories and may act as appetite suppressant). I generally limit sugar in my food, though not to zero. On my non-fasting days, I have a breakfast, but I try to have no more than 3 meals a day. No snacking. I decide whether to fast or not by the state of my hunger in the morning. If I am ravenous, I have a breakfast and a non-fasting day. If I feel only slightly empty, I go without breakfast to a total length of 17-19 hours of fasting. I am now experimenting with continuous glucose meter to find out what meals send my glucose too high. This, again, seems to be individual. Rice and potatoes seem to act really crazy. Interestingly, pizza not so much.
  - 1_player 5y ago
    18/6 has never done anything to my BP, I've been doing it for 10 years. I suspect the biggest impact was trying to lose weight and changing your diet. In my case changing my diet has noticeable and immediate effect to any physiological metric than any other "trick".

rozab 5y ago

Does anyone have any fasting advice from a reputable health authority? For some reason the NHS doesn't really have any online, even though a sizeable proportion of the population observe Ramadan. They usually have good, well-cited articles on this kind of thing.

reedjosh 5y ago
Governmental health bodies are very behind on this topic. They used to even claim fasting was terribly unhealthy.
tdaltonc 5y ago
What sort of advice are you looking for? I wrote this, most of the links are to primary research on fasting. https://usetemper.com/learn/metabolic-fitness-no-bigger-opportunity/ https://usetemper.com/learn/metabolic-fitness-no-bigger-oppo... Most of the primary research isn't really focused on generating "advice." If I had to pick the protocol with the best direct evidence, I'd pick "early time restricted feeding" (eTRF). https://pubmed.ncbi.nlm.nih.gov/29754952/ https://pubmed.ncbi.nlm.nih.gov/29754952/ That's what Brian Johnson practices. It's not a fasting protocol I would actually recommend to most people because it's pretty inconvenient, but it's been directly studied as an intervention.

frereubu 5y ago

This study is in rats, and if I'm reading the article correctly it also involves a population of rats that are bred to be predisposed to hypertension. So although it sounds like there are some interesting anecdata stories in the comments, this is very far from being generalisable to human populations. Seems like it would be a pretty easy study to do in humans though, to the point where I wonder if it hasn't been done already, even if not specifically focused on gut bacteria.

tdaltonc 5y ago
Intermittent fasting has previously been shown (in humans!) to lower blood pressure. https://pubmed.ncbi.nlm.nih.gov/29754952/ https://pubmed.ncbi.nlm.nih.gov/29754952/ https://pubmed.ncbi.nlm.nih.gov/28202779/ https://pubmed.ncbi.nlm.nih.gov/28202779/ https://pubmed.ncbi.nlm.nih.gov/19793855/ https://pubmed.ncbi.nlm.nih.gov/19793855/ Also improve insulin sensitivity, reduce glucose and/or insulin levels, improve lipid profiles, and reduce markers of inflammation and oxidative stress. https://pubmed.ncbi.nlm.nih.gov/23408502/ https://pubmed.ncbi.nlm.nih.gov/23408502/ https://pubmed.ncbi.nlm.nih.gov/27833048/ https://pubmed.ncbi.nlm.nih.gov/27833048/ https://pubmed.ncbi.nlm.nih.gov/27569118/ https://pubmed.ncbi.nlm.nih.gov/27569118/ https://pubmed.ncbi.nlm.nih.gov/23497604/ https://pubmed.ncbi.nlm.nih.gov/23497604/ https://pubmed.ncbi.nlm.nih.gov/16051710/ https://pubmed.ncbi.nlm.nih.gov/16051710/ https://pubmed.ncbi.nlm.nih.gov/23591120/ https://pubmed.ncbi.nlm.nih.gov/23591120/ https://pubmed.ncbi.nlm.nih.gov/20921964/ https://pubmed.ncbi.nlm.nih.gov/20921964/ https://pubmed.ncbi.nlm.nih.gov/27233359/ https://pubmed.ncbi.nlm.nih.gov/27233359/ https://pubmed.ncbi.nlm.nih.gov/15833943/ https://pubmed.ncbi.nlm.nih.gov/15833943/ https://pubmed.ncbi.nlm.nih.gov/15640462/ https://pubmed.ncbi.nlm.nih.gov/15640462/ https://pubmed.ncbi.nlm.nih.gov/28035343/ https://pubmed.ncbi.nlm.nih.gov/28035343/ https://pubmed.ncbi.nlm.nih.gov/25251676/ https://pubmed.ncbi.nlm.nih.gov/25251676/ https://pubmed.ncbi.nlm.nih.gov/17291990/ https://pubmed.ncbi.nlm.nih.gov/17291990/ https://pubmed.ncbi.nlm.nih.gov/22889512/ https://pubmed.ncbi.nlm.nih.gov/22889512/ https://pubmed.ncbi.nlm.nih.gov/29258678/ https://pubmed.ncbi.nlm.nih.gov/29258678/ https://pubmed.ncbi.nlm.nih.gov/25546413/ https://pubmed.ncbi.nlm.nih.gov/25546413/
- frereubu 5y ago
  Thanks for the (copious!) links.

vericiab 5y ago

I don't tend to experience hunger and, as a result, interrupting my activities to eat multiple times per day can feel like a bit of an inconvenience. So I've frequently fasted daily since before "intermittent fasting" entered the common lexicon. It's not really intentional though, I will quite literally forget to eat or otherwise just don't make it a priority. In my experience, I'm not sure it's quite the panacea it's sometimes made out to be. Perhaps there are psychological benefits to intentionally fasting that I'm missing out on. In any case, quite often when I'm wondering why I feel like shit I end up realizing something like I haven't eaten in 24 hours or in the last 48 hours I've eaten less than 1000 calories. Oops. I'm trying to be better about regularly eating 2 meals per day because I really do feel better if I've been eating consistently. I'm not sure it's doing my blood pressure any favors either. Despite regular fasting and having a BMI of 18.1 (technically slightly underweight, as the lower bound of a "healthy" BMI is 18.5), my blood pressure is usually around 140/95. But who knows, maybe it would be higher without the fasting.

dlp211 5y ago
Intermittent fasting is not the same thing as malnutrition or fasting in excess. Continually not eating for 24-48 hours and/or depriving yourself of necessary calories isn't good for anyone.

zkirill 5y ago

Fasting was one of the most memorable and shaping experiences of my life. I fasted for three days (72 hours of nothing but water) and observed so many interesting and fascinating things happening to my body each day: skin flare ups and subsequent clearings, changes in mouth and gut odour, periods of brain fog and brain clarity, cravings followed by complete loss of feeling of hunger. Every passing day had different effects. The most memorable was an astronomical improvement in my olefactory senses. By day two I was able to pick out the smell of individual ingredients in any dish being prepared in my vicinity. By day three, I lost the majority of my muscle mass. The one and only time I ever did this was when I was young and in extremely good health (daily intense exercise, excellent diet, no health conditions). Slightly worried about doing it again today. Also, quite concerned having since learned that brain mass is the first stored energy source your body will go after during what is effectively starvation. Perhaps someone more knowledge on here can comment on how true that is.

xedrac 5y ago
I highly doubt you lost the majority of your muscle mass, unless you had very little fat on your body. More likely is you depleted all glycogen stores in your muscles which is mostly water, making your muscles deflate significantly.
- zkirill 5y ago
  Maybe you're right. It was a long time ago. The only points of data that I have is that I had a "college athlete" level of fat around my heart as per my sonogram and it took me months of work to rebuild my muscle mass.
  - ekabod 5y ago
    You don't seem to know what a muscle is.