Darwinian Medicine

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I Just Finished a 40-Hour Fast. Here’s My Experience…

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lunch-timeI’ve talked quite a bit about Intermittent Fasting (IF) here on the site. Not so long ago I put up a post in which I made the case that periodic fasting was a natural part of our primal forebears’ lifestyle, and that it’s only very recently that it became normal for humans to consume 3-4 square meals a day (starting with an early breakfast). Even more recently I put up another post in which I talked about fasting as it relates to exercise, and I highlighted research showing that fasted exercise offers some unique health benefits.

I’ve also talked about the science of IF in many of my other articles. What I haven’t done, however, at least not in a detailed manner, is to describe my recent experience with fasting. Over the past couple of years, and in particular the past couple of months, I’ve been thinking quite a bit about the question of what constitutes the optimal meal pattern for us humans and why some people find that IF agrees with their bodies, while others don’t. I’ve also experimented with different IF protocols myself. In today’s article I thought I’d share some of the thoughts that this process has generated.

Breakfast: The least important meal of the day?

I generally don’t eat breakfast early in the morning. Lately, I’ve been having my first meal of the day sometime between noon and 4 P.M. Not yesterday though. Yesterday I did something I don’t do that often: I didn’t eat at all. It wasn’t planned, it just happened as I wasn’t really hungry (I ate a very large meal Friday night) and because I was occupied with other stuff (reading, writing, and socialization mostly).

When I ate my first meal today, 40 hours had passed since I last consumed anything solid. The only thing I took in during this lengthy fast was water. It wasn’t until this morning that I started paying attention to the fact that I was approaching a 40-hour fast. As I did, I got the idea that I would share some of my experiences with IF here on the site, which is what led to the birth of this article.

There are undoubtedly a lot of people out there who’ve fasted for more than 40 hours. I actually think I might have as well, in the past. But I can’t remember that experience. The point I’m trying to make with this post is by no means that doing a 40-hour fast is a remarkable feat (it isn’t). Rather, the reason I’m writing this article is simply that I have some thoughts about IF that I feel like sharing.   

My experience and thoughts: 5 key points

Note: The opinions I express below are not solely based on my experience with the 40-hour fast. Rather, they are based on my total experience with fasting, as well as some of the scientific knowledge I’ve accumulated over the years.

1) Fasting positively affects brain function

One of the things I’ve noticed over the years is that my brain function and cognitive abilities tend to be better when my stomach is empty as opposed to when it’s full. I’m sure others have experienced the same. There are many potential reasons as to why fasting has this effect on the brain. First of all, it makes sense that it was more important for our ancestors to be vigilant and mentally fit prior to eating as opposed to after eating, as they needed to be alert and smart to track down animals and get a hold of food. The behaviors of our ancestors as it relates to foraging and food intake may have contributed to shaping how the human mind operates pre- and post- food intake. Second, building on the last point, following a meal, the body allocates resources to digestive and metabolic functions. It’s less concerned about brain-related processes.

Third, meal consumption, particularly the consumption of carbohydrate-rich meals, causes a rise in blood glucose, something that could undermine brain health and function. At least I know my brain doesn’t do well on a high-carbohydrate diet. It gets sluggish. Fourth, the consumption of food is accompanied by an immune response (1). If this immune response is not well regulated, chronic inflammation may ensue, something that could obviously affect the brain via the leakage of proinflammatory compounds across the blood-brain barrier.

… but, after some time, brain function gets worse

Needless to say, brain function will eventually get worse if one doesn’t eat for prolonged periods of time. Personally, I noticed a drop in my cognitive abilities as I was approaching the 40-hour mark. I definitely felt that my brain was craving some glucose. Would this feeling have passed if I just continued the fast and my brain potentially got better at utilizing ketones for energy? Perhaps… Maybe I’ll have to go for 80 hours next time 🙂

2) Fasting can help lower inflammation, stabilize the gut microbiome, and improve appetite control

As pointed out earlier, meal consumption is associated with increased inflammation. Particularly the consumption of processed foods is problematic in this regard. The consumption of food can in some instances also perturb the gut microbiome. A lot of westerners eat a very “disordered” diet. They consume different foods and spices every day and frequently take in excessive amounts of food. These behaviors can destabilize the gut microbiota.

A fast can help remedy some of these issues and “reset” one’s body.

Perhaps needless to say, if you already harbor a degraded, unhealthy microbiota, simply fasting for 20-40 hours is not going to change that. However, it may help suppress the inflammatory fire that’s burning inside you, at least temporarily. It could also help normalize your appetite.

… but, if the fast continues for a very long time, immunity and gut health could get worse

No good thing lasts forever. Just like humans, microbes need energy to survive. If one doesn’t feed one’s gut bugs, they will eventually wither and die. A malnourished immune system is no good either.

3) Inter-individual differences in microbiota composition, diet quality, and immune status can largely account for inter-individual differences in how people respond to fasting

There’s no doubt that we humans are well-adapted to go many hours without eating. We don’t need a regular influx of food in order to keep our bodies running. Why then do some people report that they feel lousy if they fast for 14-16 hours+? Personally, I strongly believe inter-individual differences in how people respond to fasting can largely be accounted for by inter-individual differences in microbiota composition, diet quality, and immune status.

A person who eats a species-appropriate diet, harbors a stable microbiota, and has a well-functioning immune system is much better equipped to endure semi-long periods of food deprivation than someone who eats a species-inappropriate diet, harbors an unstable microbiota, and is chronically inflamed. There are many reasons why this is the case. Among other things, due to the disordered state of his gut microbiota and the chronic inflammatory processes in his body, the latter person may get regular cravings for unhealthy foods and feel sluggish and fatigued. Moreover, his liver’s ability to produce glucose may be compromised.

Personally, I’ve noticed that there is a close connection between my microbiota/immune system and my food cravings/dietary behaviors. During periods when I don’t feel so great, my body is markedly less willing to go long periods without food.

Many contemporary people are used to consume a very carbohydrate heavy diet. Hence, their bodies’ ability to utilize non-glucose nutrients for fuel is compromised. These people may find it difficult to go long periods without eating, particularly if they are used to always consuming a carbohydrate-heavy breakfast early in the morning.

4) It feels weird to eat after a 40 hour fast

One of the things I noticed as I broke the 40-hour fast with a large meal right before I sat down to write this article is that it felt a little strange to eat again. It’s like my gut and brain didn’t really have a clear idea as to how much food I should take in. I could definitely feel that the fast had had an effect on my body.

5) It’s not healthy to eat all day long

When I was younger, I always ate shortly after I woke up in the morning. Not because I was always hungry in the morning, but rather because I had been misled by conventional wisdom into thinking that it’s important to get some nutrients into one’s system early in the day. If I wasn’t hungry, I pretty much forced some food into my body.

Perhaps needless to say, this approach didn’t get me very far. It’s truly perplexing that we humans have somehow gotten the idea that it’s healthy to eat a bowl of cereals at 8 A.M. every day. From an evolutionary perspective, this is a very abnormal practise.

I can definitely feel that my body functions better if I give my digestive system a rest every now and then. I’m not sure I’m going to do another 40-hour fast any time soon though, as I’m so fond of eating. If I am to do a really long fast, I like to have a lot of stuff to do so that I don’t get bored and start thinking about food. Another thing that keeps me from doing 24-hour+ fasts on a regular basis is that my body doesn’t always feel up to such a task.

Now I want to hear from you: When do you typically eat your first meal of the day? What’s the longest fast you’ve ever done?

Reader Interactions

Comments

  1. 8 days on juice, 5 days on water. Two seperate fasts. Both killed me in terms of the constant craving for high fat foods. Torture! I don’t do well, like some of my friends do (30 days happily and easily on juice), for me it’s a battle as I crave and think about eating ALL the time! Maybe this one will be better. Just at the end of day two, but to make it easier and more likely ill go the distance I’m adding bone broth to the equation – juice and bone broth with water fasting days in between. So no solid foods just liquid… More of a reset than a fast this time.

    Reply

    • Lucy, you’d be much better off eliminating juice from your fast. Fruit juice is very, very high in fructose (Google sugar content in juice) and contains no fiber to slow absorption into your blood stream. This causes your blood sugar to spike which your body has to work very hard to counteract by dramatically increasing your insulin levels. Your pancreas will often overshoot insulin production (reference: http://www.nutritiontotheedge.com/how-blood-sugar-affects-your-health-and-energy/) which will then cause your blood sugar to go too low. This is known as a sugar crash or a carb crash (this happens with breads, pastas and other refined carbs, too). This will cause cranky Lucy to come out to play. And nobody likes cranky Lucy. Next time you fast, go water only or water and bone broth. You should find fasting to be much easier. Best of luck to you.

      Reply

      • My ‘juice’ is usually 80-20 veg to fruit sometimes it’s 90-10 Robert. And I’m never cranky… not since I gave up the refined carbs years ago. What I crave is meat and fat and cheese. High fat. And it drives me INSANE if I water fast. I literally can’t think of anything else! That’s why the “juice” is good. It’s enough to stop the insane food craving. I may not be going as deep as with just water, so it’s more gentle and doable and i can stick at it longer. Its not very Darwinian to juice, but our ancestors could have come across a fruit or a plant and squeezed the liquid out… Who knows! I’m starting to think we went from hunting and gathering to settled grain farming just because man discovered how to brew beer, so maybe it was all about getting pi&&ed, this great leap forward! Wouldn’t that be ironic!

        Reply

  2. I fast 14 to 16 hours on a daily basis. I usually eat breakfast around 10 or 11 a.m. and dinner around 6 p.m. (sometimes earlier) with nothing afterward. I usually eat twice a day and have no desire to snack between meals. I eat this way because it feels right to me. I have no desire to fast for longer periods of time. Everyone is different, but for me personally, I don’t feel it would be of any benefit.

    Reply

    • That’s just about exactly what I do and I function very well on that routine. Even on a Saturday morning — I play volleyball from 9:00 am until 12:00, so only eat about 1:00 pm. But I feel great. In retrospect, though, I guess I am actually not completely fasting until lunch, because I do have a cup of coffee with a giant tablespoon of coconut oil. It still works well, though.

      Reply

  3. Same here 🙂
    My first meal is lunch between 12 – 1 pm, then I have one or two other small meals until 8 pm latest, mostly it is 6 pm.
    I do this since the end of last year, and I do no ‘binge-eating’ anymore. I had such attacks very often before, and it was not nice.
    Now I lost 14 pounds (is that right? We say 7 kg in Germany) without eating healthy “rabbit food” only. 😉
    I still do eat what I want, even some fries or cake sometimes. But I don’t have as much craving for sweets or snacks as I had before. Now I have more vegetables and fibre, because I really WANT it. I don’t have to force me to do that, it came automatically.

    I feel definitely better with intermittent fasting than before, it changed my eating behaviour and I lost weight. This is my personal experience.
    I would not claim that it would be good for everyone else, but if you think it could, give it a try. 🙂

    Reply

  4. I have in the past fasted for a couple of days without too much trouble. It helps that when I did it I was pretty well fat adapted by having been quite strict Paleo for a number of years, so I never really craved carbs. Another vital thing was that I was very well rested (two of these fasts took place on holiday) and I kept myself busy. If I ate at 8 pm one evening, it actually wasn’t that hard to go on all day and sleep that night, and the next day it was both a battle of boredom and will power to see how long that day could last. I think I might have managed going through a second day too. It was always more a mental issue than a physical one – it felt a bit weird, to be honest, not to eat.

    Reply

  5. Personally, I feel there is enough scientific evidence to prove the benefits of fasting. The issue comes down to how you get a fast to work for you personally – as many of the above posts show.

    I’m no expert but I have done a lot of fasting. I have done 7 day juice fasts, water fasts and a 30 day green juice fast. After detoxing, I also did a 10 day dry fast – no food or water – yes, you can survive without food and water and nope I didn’t die! In fact if I had had the time I knew that I could have gone much longer (and boy does food taste amazing when you – carefully – reintroduce!)

    The two factors that I feel make a fast successful are:
    1. Find a way that works for you. Either every day in your normal routine and/or periodic fasts and/or fixed time period fasting and/or retreats and/or 5:2 etc. Remember, all the time there is no food for the gut to contend with, it can get busy doing it’s proper job which is eliminating, healing and repairing. Our gut wasn’t designed just to deal with food, in fact that should only be a small part of its job. There is no doubt fasting is amazing. Just see how your skin and eyes change and start to glow when you do a prolonged fast.

    2. However, fasting is often not amazing because we start with a full gut and we detox faster than we poop out the toxins our bodies want to eliminate. This can mean you crave foods, you get headaches, you get nausea, you feel exhausted, you feel emotional or any combination (and more) of these. My experience and logic has shown me time and again that unless you ensure that the toxins which your wonderful body has been busy dumping into the gut for elimination are actually eliminated, then they will sit in your gut and they gradually get re-absorbed. This is why I have yet to see any red wine or cofffee drinker be able to fast without problems.
    The answer – which may not be attractive for some – is colonics or enemas. Do one or other at the start of your fast and get it all cleaned out. That way there is nothing left in the colon for the body to re-absorb and cause cravings plus the healing and repairing can start right away. Then do another part way through your fast so that the toxins your body is expelling get out and don’t get re-absorbed and make you suffer. Then at the end – as a final clean out. If you are just fasting daily but still eating eg 14 hour or 5:2 type fasting then you won’t tend to get the more hardcore symptoms and won’t need to do this. But for juice/water/prolonged/dry fastings I honestly believe this is the key to success. And for those of you who may worry about a tube being inserted where the sun don’t shine – you have to weigh up what’s more important – your health or your restrictive mindset. It’s really no big deal. In fact, once you’ve done it you really wonder what all the negative fuss is about.
    There is nothing like a good colonic or coffee enema in the same way there is nothing like a good fast. Sometime you can just do the former without needing to do the latter. Just always take care about how you introduce foods back into the body after either colonics or fasting. You don’t change the brakes on your car and then go drive at 150 mph – you bed the brakes in. Treat your body as if it were a car far more incredible and valuable than even a Tesla or McClaren or Lambo! We change the oil in our engines by draining and flushing – why wouldn’t we do the same for our bodies given how much more wonderful they are!
    Just some thoughts which I hope may help.

    Reply

    • Hi Corrina. My main question would be “Why?” Why would you assume your body is so filled with toxins that your liver, kidneys, lungs, etc. are unable to do their job of keeping you healthy? Why would you think depriving your body of water (which is essential for life itself as well as good health) is really a good idea? Do you have intractable health issues, or are you just convinced that interfering with your body’s natural processes (via colonics and coffee enemas) is necessary?

      Unlike a McLaren, the healthy human body is self-cleaning and rarely, if ever, needs help with it, other than through diet and lifestyle adjustments.There is no medical science that I’ve ever heard of that promotes the regular use of detox products or unnecessarily long fasts. I don’t mean to sound preachy or argumentative, but truly, your logic escapes me.

      Reply

  6. I am at hour 24 of a 40 hour fast. I feel fine. At hour 20 I beagan to get very hungry but after drinking about 12 oz of water the hunger subsided. Also I was preparing the weeks meals during that time. I am glad I didn’t break down and eat at that time. One of my main objectives for the 40 hr fast was to increase discipline and confidence. Full disclosure; I practice 18/6 IF regimen daily and have for about two months. I have constantly lost weight and body fat since beginning the IF protocol. One of the reasons for weight loss is that it is difficult to over eat when you restrict your hours of eating. I also exercise in a fasted state daily. This is the best I have felt in years.

    Reply

  7. I’ve recently begun incorporating a 36-40 fast twice a week. I’ve found that once OVER the 24hour (for some reason that’s when my body argues it wants food) mark, my energy is heightened, and I have mental clarity and my hunger abates. I agree the first meal back after a long fast is an indecisive moment. “do or don’t I” want to eat. I usually break with a frozen berrie smooshie. I am currently at the begining of my end of week long fast, so I won’t eat till Saturday morning. (I am a breakfast eater, I prefer eating earlier in the day rather than later always have, lunch and dinner have never been priority.) But so saying I do for the rest of the week sit on 20///4 fasting/eat protocols. I decided to incorporate two longer fasting days just to see if it makes a bigger difference, in clarity, weight control and health. So far I’m happy with the three time I have done it. And actually look forward to it… So yes the occasional longer fast is working for me.

    Reply

  8. I am just about to break the 40 hour water fast i do once a week. I don’t find it difficult, nor do i get headaches, cravings or other unpleasant symptoms but at some point i start to feel weak and lethergic and that picks up as time continues. I am amazed by people who do 7 day water fasts and carry on as normal. I’d have to take to my bed if i were going to do that.

    Reply

  9. Currently travelling and I contacted a stomach bug in South Africa with the most severe stomach cramps and extreme diarrhoea. I was admitted to hospital and given morphine for the horrendous pain.
    Obviously medication was prescribed by the medical staff but my wife who knows everything including how the universe originated demanded that I fast.
    Advised not to eat anything for 40 hours.
    I’m currently into 30 hours without food but drinking water and electrolytes.
    Last 10 hours I’m feeling so much better, lacking some energy but alert and not hungry.
    HOWEVER, this next part is interesting.

    I’ve been suffering from PMR for some time which attacks the immune system developing in unbearable sore joints and muscles and all I do is sleep during the day. Steroids are the normal medication given by Doctors but they make me horrible sick .
    At 30 hours of fasting I’ve had no symptoms at all from my PMR which takes years to overcome.
    I was on 30 mg of Prednisone but last two days I reduced it to 12,5 mg. when I started to feel unwell.
    Also the bloating around my ankles has completely disappeared during the last few hours. My ankles were so bloated from the steroids that the photos of oversized ankles became a FB hit.
    Even though the extreme diarrhoea has obviously weaken me, I’ve got more energy at the moment than I’ve experienced in a month.
    Your articles on the benefits of fasting are incredible informative and I do thank you sincerely for this opportunity.
    I’m not saying I’m cured of Polymyalgia Rheumatic (PMR) however this is an interesting development .

    Reply

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