Dorion Mode - A blog by Robinson Dorion.

March 7, 2023

Prolonged Periods in the Postabsorptive Phase

Filed under: Salutem — Robinson Dorion @ 16:09

My first foray into fasting, aka the postabsorptive phase, started sometime in 2015 or 2016. I was listening to a Tim Ferris podcast in which he had someone read an English translation of Lucius Annaeus Seneca the Younger's Letter XVII on Festivals and Fasting. What initially caught my attention was Ferriss's introduction in which he said something to the effect of, "sorry if my throat is a bit scratchy, I just got done with a 10 day water only fast." This struck me because as someone who had been eating three meals a day with some snacking in between for a couple decades and a half by then, fasting wasn't something I had really considered. I was aware of its practice in various religions and such, but I didn't grow up with those observances. I started looking into it further and come to find that some people go much longer than 10 days and that there exist so called fasting retreats where people go for months without eating !

Exploring the topic further, I came across anecdotal reports of people experiencing beneficial results in curing various cancers and auto-immune diseases and beyond. While the skin may be the body's largest organ, counter-intuitively, the digestive tract, from food hole to asshole, exposes the greatest surface area of the body to the external environment. It turns out that when you give your digestive system a rest, your ability to heal substantially improves, at least for a window in which you still have adipose reserves to consume. When new calories aren't coming in, the body starts economizing and autophagy(i) kicks in, which tends to first target damaged and pathogenic cells for consumption.

Despite having a clean bill of health, it piqued my curiosity to see what it's like to take a break from eating. I started experimenting by skipping breakfast, then breakfast and lunch and then moved up to 24 hours fasting and eventually a couple days. In 2017, I went five days fasting. It was a pretty cool experience. After 24-36 hours, the feeling of hunger subsided. A part of you wants to eat, if out of habit more than anything, so it becomes an exercise of will because you know if you break it, it's going to take you another day or two to get back to the same spot so just keep going and get it over with already.

Let's dive into some of the physiology since 1) we can and 2) knowledge of the underlying processes makes the practice easier to bear. The homeostatic blood glucose range the body aims to maintain is 4-6 mmol/L to supply the brain and other tissues that need it for energy. As new calories stop coming in, there's a brief window of muscle metabolism, but after a short while, the body decides to save the muscle tissue and switches to tissues that are harder to breakdown, but less important for survival. From the Alpha cells in the Islets of Langerhans(ii) in the Pancreas a peptide hormone called glucagon is synthesized and secreted. It's also synthesized and secreted by the duodenum section of the small intestine. Glucagon has several functions which include :

  • stimulating the release of glucose from the liver to the blood ;
  • stimulating the enzyme glycogen phosphorylase which promotes degradation of glycogen into glucose ;
  • inhibiting the enzyme glycogen synthase which synthesizes glycogen from glucose ;
  • stimulating gluconeogenesis which is the process of converting glycerol, glycogen, acetyl-CoA, pyruvate and oxaloacetate into glucose via the enzyme glucose 6-phosphatase ;
  • stimulating glycogenolysis which is the process of converting glycogen to glucose and happens in the earlier stages of fasting and is overtaken by gluconeogenesis after about 20 hours ;
  • stimulating lipolysis which is the degradation of triglycerides in adipose tissue into free fatty acids and glycerol. The free fatty acids can be utilized by the heart and skeletal muscles and are also sent to the liver to be converted to ketone bodies. The glycerol enters the liver for gluconeogenesis ;
  • stimulating the conversion of fatty acids to acetyl-CoA and then acetyl-CoA to glucose ;
  • stimulating proteolysis which is the conversion of proteins in the liver to amino acids which are fed into gluconeogenesis to glucose-6-phosphate and then to glucose ;
  • stimulating degradation of triacylglycerol to glycerol (then to glucose via gluconeogenesis) and fatty acids via hormone sensitive lipase ;
  • stimulating ketogenesis which is the process of converting fatty acids to ketone bodies, which are used as a source of energy for the brain and skeletal muscles.

Glucagon pretty well covered, let's dwell a bit on the last point. In the early fasted state, there is a decrease in blood glucose and increase in free fatty acids. However, free fatty acid levels do not surpass blood glucose levels at any point. When fatty acids enter the liver, they're oxidized, via beta oxidation, to produce many acetyl-CoAs. There is an abundance of acetyl-CoAs accumulates such that they can't all enter the Krebs cycle like they normally would. The substrates within the Krebs cycle, such as oxaloacetate, are already used as energy to feed gluconeogenesis. The Krebs cycle becomes backed up, but glucagon comes to the rescue and stimulates ketogenesis and converts the excess acetyl-CoAs to ketone bodies, which can then be used by the brain, heart and skeletal muscles. There are three types of ketone bodies : beta-hydroxybutyrate, acetoacetate and acetone.

The brain always uses glucose in the absorptive (fed) state, but after 2 days, 70% of its fuel comes from glucose from glycogen and fats and 30% comes from ketone bodies. After 2 days, ketone bodies increase significantly and surpass blood glucose levels within a week. After weeks of fasting(iii), the ratio in the brain flips and 70% comes from ketone bodies and 30% comes from glucose. At the heart, brain and skeletal muscles they're converted to acetyl-CoA and enter the Krebs cycle to produce ATP as energy and CO2 as waste.

If you go what's beyond healthy in your fast and start starving the proteins in muscle will eventually start to be broken down into amino acids and enter liver for gluconeogenesis which produces ammonia (then urea) and glucose. The muscles are the second to last to be broken down, last comes internal organs. The kidneys are also a source of gluconeogenesis and after weeks become the primary location after the liver falls behind in keeping up with the body's glucose demand. I highly recommend fasting, but starvin' like Marvin, not so much.

Another thing that happens when you're a few days into a fast is a protein called Brain-Derived Neurotrophic Factor (BDNF) spikes, which sharpens your mental acuity. Which makes sense from an evolutionary perspective. Our hunter gatherer ancestors weren't on the three meal a day lifestyle and often went days without a kill. The ones who managed to pass their genes to us were the ones who found focus in the hunger and ended up bloodying their blades.

Furthermore, when you don't eat, you realize how much time and energy eating and its supporting and consequential tasks take : from buying food, to cooking it, to cleaning up after and shitting it out and bideting yourself off. It's a nice little vacation that frees up some time and mental energy.

When I did my 5 day fast back in '17, my lack of excess reserves was the limiting factor in that case and doing it more often generally. For most of my life, I didn't have the easiest time gaining and keep weight, to the point that one of the nicknames Coach Norman, the Raider football coach, gave me was, "Skeletor"(iv). After 5 days, I tried to go to bed with a plan to breakfast the next morning, but I couldn't fall asleep. I felt like I had loads of energy, but I also suspected I had started to metabolize more muscle, which I wasn't keen to do. So, I broke it with some dates and some almond milk and slept soundly.

One definitely wants to be careful breaking a prolonged fast. It's imperative to fight the urge to munch a mega meal right off the bat. Ease into the eating and take your time, let your system readjust to food and savor the flavor.

Fast-forward to this year and I had done intermittent fasting on a semi-regular basis in the interim, but no prolonged fasting. After a couple months of fairly(v) strict Carnivore diet, not so much exercise (but not none) and feasting and imbibing during the late fall festivals, I found myself to be the heaviest on record at 80 kg. Certainly far from fat, but excess reserves to metabolize I had !

So, I had a big meal with friends at Maguro(vi) the night of January 4th and waited until the evening of January 11th to breakfast. I continued about my days as normal, but with reinstalling the old habit of exercising first thing, which I've kept consistently to date. When Jacob arrived the 8th, I sat with him and Fausto and drank water as they ate steak and eggs for breakfast. On Tuesday the 10th, we went to a dinner at Da Stefano's with a group primarily composed of Bitcoiners soft-forkers, some of which might be converted to Bitcoiners, someday, maybe. I drank Perrier and watched them eat. It looked and smelled great and I'll definitely be back with my appetite. Hanging out with people while they eat and you fast might not be for everyone. It wasn't hard for me, perhaps it's all that time I spent sober around people who were boozing, YMMV. My lowest weight in the cycle was 74.5 kg. I broke it Wednesday evening with a couple cups of homemade bone broth and a small slab of beef tenderloin. Feeling I had digested those okay, I had an orange then an apple. I had a smaller(vii) breakfast the next morning and then it was back to normal eating. I could've gone longer with the fast, but a group of friends had plans for an Indian food lunch on Friday and I realized that I didn't need to be a hero and go another 12-24 hours. I can always go another seven days next quarter or so if I still have excess reserves. I quickly gained back about half I had lost, likely do to greater water retention with food in my system.

It's a good idea to continue your resistance training regimen while you fast. It turns out, growth hormore spikes significantly during this time. Also, mind your sleep, you want to be getting plenty of it because if not, you'll metabolize muscle rather than fat. It was a good mental and physical exercise to start the year and I expect I'll do it again in a few months. For next time, a couple refinements I'll make are :

  1. Work out harder the first 12 hours to deplete glycogen levels and get into ketosis faster.
  2. Get a kit of test strips to verify when I'm into Ketosis.
  3. Take some circumference measurements to have further physical data points apart from weight.
  4. Get some blood panels before and after.

So here's to fasting and never being a fatty --or at least not for long. Which, if you're honest and aren't one to discredit logic, you realize by now obesity is purely a choice, buen provecho !

P.S. It's fun to write articles which end up adding new words to the spell checker. Ol' aspell was unaware of most of the medical terms, "Ah, no, we need a medical dictionary !" right Kramer ?

  1. A word English inherited from Greek via French which means self-eating ; ancient wisdom this is. [^]
  2. There are 5 distinct cell types in these Islets, which are named after the German who discovered them in 1869 :
    • Alpha cells range from 15-20% of the cell population and secrete glucagon ;
    • Beta cells range from 65-80% and secrete insulin which regulates the metabolism of macromolecules and amylin which regulates gastric emptying to prevent spikes in blood glucose levels ;
    • Delta cells range from 3-10% and secrete somatostatin which regulates pancreatic hormones ;
    • Gamma cells range from 3-5% and regulate both endocrine and exocrine secretions ;
      • Endocrine glands do not have ducts and secrete hormones directly into the bloodstream, examples are : thyroid, pituitary, adrenals, liver, pancreas.
      • Exocrine glands have ducts and secrete sweat, enzymes, mucus, sebum to an internal organ or the external surface through a duct, examples are : eyes (tears), Ceruminous (earwax), mouth (saliva), skin (sweat & sebum), tits (milk), stomach (enzymes), liver (bile), pancreas (juices).
      • The alert reader will note the liver and pancreas appear on both lists ; that's right, they're both at once.
    • Epsilon cells make up less than 1% and secrete Ghrelin, a protein that stimulates hunger.

    So it's not just in natural human populations where the Alpha wants to be left alone, but in the Pancreas too ! As above so below ; as within so without. [^]

  3. Or depending on how much reserves one has. Side note : instead of estimating a fatty's weight, it's sometimes fun to estimate how long they could go without eating. For example, a good chunk of the population in USia could likely go a full year and probably upwards of half the population could go at least a quarter without any eating. Put the magic pills down and try it sometime why don'tchya ? [^]
  4. He looks kinda jacked in the pics though, amirite ? [^]
  5. I'm not really cooking carbs myself, but when I'm invited somewhere or out to eat I'm not being a meat snob either. [^]
  6. Which I'm told by someone who knows, it has some of the best Otoro around -- not just in Panama, but globally. Buddy is a pretty dedicated foodie, went to Japan to learn to make proper sushi, for example. I can vouch their service works, which isn't often the case in Panama. I'd link to their site, if they had one, but apparently they only have platform presence... [^]
  7. Two eggs instead of five and more beef. [^]


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