The best kind of motivation is the kind that just randomly shows up for free. I'd be foolish not to take advantage. 

I got hit with the random urge to do a 2 day fast, so it was the best time to do one! It's been a few years. I did get hungry on the first day and had a small amount of calories but considering at my weight the maintenance level is still about 3000 cals/day it was still 93.3% successful, roughly!  

Anyway, since I need to do some research occasionally, I decided to collect information about fasting. there's a lot of proponents to this practice, and say you should be doing these regularly. Here's why.

Benefits of Fasting High-level:

I've you've tried fasting for 2 or 3 days, you might have felt it. It's been several years for me but I still remember how excellent I've felt waking up in the morning after 2 days of not eating. It turns out there's a lot of actual physical reasons for this, from shifting your metabolism into a more youthful state, to resensitizing your brain to dopamine, to cleaning out inflammation. Don't worry, I will cover it all in painstaking detail haha.

But dopamine, insulin, inflammation and HGH aren't the only benefits. Autophagy - gettin' rid of old body gunk on the cellular level - is the main one I'm after, but there's also Ketosis, Other Brain Benefits, Stem Cell production, Longevity Benefits, Insulin Sensitivity, Stem Cell Production, Fat Adaptation, all kinds of things. There's really a lot that happens.

The short of it is there are just things that your body only does when it's in a low food state. I'm sure there's various biological reasons for it, but that that's just how it is. And it turns out, for a controlled fast, most of these things are beneficial! Not all of them. You do burn some of your own muscle. If you aren't careful and put the weight back on, (and your body's gonna want to, there's various reasons for that too) it could be really bad for your long term goals too (I should . So care must be taken after the fast to keep the success going! Be prepared and if it's for a diet, well then take care not to relapse. In fancy terms your body and brain pathways and hormone signals will cause you to feel the need to "seek homeostasis". However, we are humans with functioning brains, and we have a thing called a prefrontal cortex that can help us use willpower until we adapt to our new state. Or so they say haha.

Benefits in Depth: 

Note: Human Bodies are rather complex things with trillions of cells all doing uncountable numbers of chemical reactions constantly at all hours of the day. No two are the same. However, these are the typical benefits that the majority of people can typically expect. 

If trying fasting yourself, make sure you're good with a single day first, before trying to go longer. I already know I am so I'm good to go. 

Anyway, here's the skinny on many of the interesting benefits:

Resting Digestion: The digestive system takes up a lot of body energy. Stomach and intestinal linings need to regenerate every few days. Other related things, glands and such, are regenerated frequently, not every few days, but frequent enough to be notable. The benefits to resting digestion include better repair, rebalancing the microbiome of your gut (and the mind-gut connection improves as well), as well as your body, at least in the short term, using the energy normally involved in digestion to do other things around the body as well. I'm sure the way it works is very personal, but for me personally, I feel like I have a bit more mental energy (of which I usually spend thinking about food haha).

Ketosis: If you're getting into fasts or dieting you'll see this term thrown around a lot. Here's what it means. When you eat, especially carbs, a lot of of the food gets broken into glucose, then gets absorbed into the bloodstream through the small intestine. Inulin (more on that later) spikes, this chemical tells your cells to start absorbing the glucose. Some of the food gets converted into glycogen (a big molecule made out of a lot of glucose) and stored in the liver but once the glucose and glycogen runs out (can take the better part of a day) the body starts shifting to breaking down fats. The fats break down into chemicals called ketones, and cells start using this for energy instead. This body state is called Ketosis.

I think the body has to build up to this or get use to it, as sugars and carbs are in everything and for many of us (myself included) we're just used to having that glucose all the time. I remember when I first lost a bunch of weight (something I've done several times now, for me the challenge is just sticking with it) I felt kind of faded out during the start when I started dieting. Like my mental function would just go down to 50% now and then and get fatigued (what's 50% of nothing again?) I just think my body just wasn't used to not burning glucose. 

But the body can Adjust! I know I adjusted and it doesn't really happen now. And burning ketones as opposed to glycogen all the time is generally healthier as well.  Once the adjustment is made you could see more consistent energy levels (being less sensitive to blood sugar fluctuations) and be less prone to physical and mental crashes. But you can also adjust back quickly too however, so take care!

Insulin Resistance: Closely related to burning glucose is Insulin. Insulin helps your cells take in glucose to burn. Glucose is a form of sugar, and you might have heard of "blood sugar levels". Well when you've got a lot of glucose floating around in your blood, you've got a high blood sugar level. Your body will then pump out insulin, which helps your cells take up this glucose to burn. 

Insulin Resistance is when you become less responsive to insulin in your blood. What fasting does is DECREASE insulin resistance, that is, your insulin gets super low, so your body adapts to become MORE sensitive. This leads to multiple things once your body adapts: your insulin levels stay lower, blood sugar stays more consistent, and cells become more efficient in reacting. Overall, like the effects of ketosis, you should expect more consistent and efficient energy, with less peaks and valleys, as well as it's generally better for you on a cellular level. 

Growth Hormone: Another banger adaptation your body does adapt to a low-food state is it starts increasing growth hormone which is also referred to as HGH. HGH assists in tissue repair, muscle growth, metabolism (in several ways), cellular repair, and possibly (likely) enhances mitochondrial efficiency (and we all learned in high school that the mitochondria is powerhouse of the cell. Actually that untrue, I saw it in a meme. But it's true it's probably the most important powerhouse, producing the energy that all the processes need), and also stem cell production (stem cells are the basis for shiny, healthy new cells). It also decreases inflammation. But is anything in biology ever super simple? Too much or chronically high HGH can increase inflammation, however, just bumping it temporarily seems to be very beneficial. And it's not just a slight bump, after 2 or 3 days the levels of HGH can get to several times the normal baseline! I think it's possible medically to get HGH injected but it's expensive. With a little bit of fasting, you can save thousands on HGH injections (and also a little bit on food! Since I just saved you thousands, it's ok if you feel free to send me some cash in gratitude) 

Mitochondrial Biogenesis: Ketones in your blood trigger several known processes that ultimately tell your cells not to only get rid of old mitochondria, but also create new mitochondria as well. Mitochondria produce energy for the cell to use through a process known as ATP. This is worthy enough to mention on it's own - healthy mitochondria keep the cell functioning longer.

Autophagy: This is a process that cleans out damage on a cellular level. Going back to Mitochondria, damaged mitochondria can really mess up a cell. (Getting rid of mitochondria is called mitophagy) So can misfolded proteins and other stuff like that, autophagy is a process that starts cleaning these out. But beyond that, there are things in your body called sentient cells. Also referred to as zombie cells. These are cells that no longer function, they don't divide, what the do is just sit in your body messing up the neighborhood around them. They put out stuff that damages other cells, they can cause inflammation, they can even turn cancerous. You want as few zombie cells as possible, and during a state of autophagy, your body starts cleaning them out! Even better, the process that takes out zombie cells, apoptosis, can signal stem cells to activate.

Stem Cell Activation: Stem cells are basically cells that can become other cells, all brand new and shiny. You never stop making stem cells, but your production decreases the more you age. Might as well use the ones you got, right?! Apoptosis, cleaning out the zombie cells during Autophagy, signals these cells to activate. Most notably, these stem cells can boost your gut and your immune system, two y'know, very very important systems, but your body can actually send them anywhere they're needed. Cold exposure can also increase stem cells, and decrease inflammation too. Are cold showers and cold plunges still a fitness trend? I don't even know haha. I don't gotta worry myself, I'll get plenty of THAT during winter here.

Brain Boost: BDNF (Brain Derived Neurotropic Factor) - it basically boosts brain connection and it gets produced... yep, during fasts. It can prevent brain disorders (dementia, Alzheimer's, even brain fog). Neuroplasticity, neuroprotection, learning capability, and resilience increased. There is also more mitophagy (producing new mitochondria - for some reason I can never remember that word) and guess which cells have the most mitochondria by a long ways: brain cells! The mitochondria refresh and the BDNF are a one-two punch for increased brainpower. You want to be smrt right? (is that how it's spelled?) Well with fasting you get that brain boost. But wait! There's more!

Dopamine Resensitization: Taking drugs and doom scrolling social media all day and still feeling numb? Your dopamine receptors in your brain could be desensitized. During a fast, they can be resensitizatized. Dopamine is a critical brain element for when things feel good. I wonder if it has anything to do with making food just taste so good after not eating for a while haha. Moreover, being sensitive to dopamine can help in drive, focus, motivation, mood, energy, just about everything good. This happens typically after the first 24 hours, so it's one of the effects that you gotta fast for a while to get haha. 

Inflammation Reduction: The Ketones, drop in Insulin and Glucose, and Autophagy all contribute to a reduction in inflammation, I think the stem cell activation can contribute too. Like zombie cells, inflammation is something you don't want too much of. It's ok when it's for defense and healing, but extra inflammation is detrimental. In fact, fasting can even help with chronic inflammation according to what I've read, so throw that onto the pile of benefits!

Longevity: All these benefits add up to keep you living longer! Which makes sense, your lifespan typically is correlated to health. Interestingly, the lower insulin, higher HGH, increased stem cells, and increased autophagy is considered to be a metabolic state that more resembles a "youthful" one. But all the effects can help you out in life, from brain and dopamine boosts, to decreased inflammation. Stay biologically younger longer, and live longer as well!

Types of Fasts

The concept is simple, just skip eating for a while. However, there are various types of popular variations that people use.

Coffee Fast: No food, but coffee (black, without additives) is ok. Coffee can reduce hunger slightly, and doesn't seem to significantly disrupt the benefits of ketosis or autophagy

Water Fast: Only water is allowed.

Dry Fast: No food or water. The body gets it's water from fat breakdown. Can strain the kidneys, cause dehydration, or be dangerous if prolonged, so I've seen lengths longer than 24 hours be discouraged. The autophagy may be more rapid with this type of fast.

Olive Oil Fast: a couple tablespoons of olive oil are allowed several times a day. Olive oil doesn't interfere with ketosis, staves off hunger, but might be slower to trigger autophagy. But I've also seen that extra virgin olive oil - the real early harvest type (usually has a bit of a peppery kick) - has a chemical that can trigger autophagy, so depending on the qualities of the oil, I've seen it claimed that it could possibly start autophagy earlier. So the jury might still be out on the exact effects of this one! While looking this up I found a video recommending combining olive oil with MCT and BHB (beta hydroxybutyrate) so this one is on my radar and I might give it a try one of these days.

Fast Mimicking Diet: A prolonged, 5-day or more, low calorie diet. Low protein, low carb, high fat. It keeps several hormones low, which in theory "tricks" the body into thinking it's fasting. The advantage is that it's a bit easier than a hard fast and promotes lean muscle mass. 

Intermittent Fasting: A form of dieting that has gained traction, strategies including one meal a day or holding yourself to an 8 hour eating window. I'm seeing it used for weight loss, but it's also said to convey the benefits of fasting.

Juice Fast: Only Juice. Rests your digestion, which I've seen described as a good thing, but I'm not sure exactly what that alone does. Can be calorie restrictive while you still get nutrients, but you don't get insulin resistance or autophagy. 

Bone Broth Fast: Like a water fast, but with bone broth. Sounds like a slightly tastier version of a water fast. For me, I suspect it might trigger my appetite though haha.

Tea Fast: Like a water or coffee fast, but with non caloric herbal teas. 

Jesus Fast: (must be done in a desert) No food for 40 days and then the devil comes out to tempt you to use your God-like powers. If you can't take 40 days off work, it can be simulated with hallucinogens. 

Fasting Timelines

0-6 hours: During this time you're still being fueled by the glucose from your last meal.

6-12 hours: You start using glycogen for energy. All the factors I mentioned in the benefits gradually start activating. It is common to feel hungry during this time. 

12-18 hours: You start running low on Glycogen, and your body starts shifting to breaking fat down to ketones. HGH starts going up, Autophagy, Mitophagy, start kicking in, BDNF starts elevating, dopamine starts rising (it's nature's way to keep you focused on looking for food), and typically measurable inflammation indicators noticeably drop. 

18-24 hours: Ketosis continues to rise, HGH is spiking, Autophagy and Mitophagy are kicking in, Insulin is very low, BDNF is continuing to rise. Hunger may decrease although for me it is still pretty high.

24-36 hours: Insulin drops to near baseline, all the other factors are heightened, and ketosis is still rising. Hunger should start decreasing, I can attest to that, although for me it is still present.

36-48 hours: ketosis is in a high state, although it's still going up. Dopamine sensitivity is good, inflammation is very low, all the other factors are still all in high gear. 

48-72 hours: Stem Cells typically activate the most during this period, and ketosis is at it's peak. HGH is extremely high, Insulin is extremely low, BDNF is at it's maximum, and many influencers and enthusiasts and well, internet videos describe between 2-3 days as the optimal length to fast. But you gotta work up to it. I'm still working up to 2 days myself haha but I want to try to do some 3 days one eventually. Hunger should be low again, and your appetite mechanism should be resetting.

40 Days: (only works for the Jesus fast) the devil should appear before you and tempts you to use your powers. However, if I am interpreting scripture correctly, in order to succeed you must break the fast on your own terms. Do not let the prince of darkness interfere with your goals! 

When to Fast?

And finally, one more question. What is the best time to fast? I'm seeing once a month pop up as general advice quite often (usually the influencer also does intermittent fasting as well, but you do you. Me, I'm just gonna do what makes my body feel good while I do this weightvest running thing). For Men, I guess, whenever it's convenient or you're feeling motivated. For Women, anytime is fine except the week before the mensural cycle (I've seen advice that during the mensural cycle is actually a good time but I don't have a lot of sources on that)

Anyway, that's the result of my research on fasting. I may update this article as I'm always reading more haha. 
 

My Experience

Well, like I said, I made it through most of the first day. Then I remembered I had tasty leftovers in the fridge. I'd guess about 400 calories haha. The 2nd day I made it. Felt great on the 3rd day. Down nearly 3 lbs in 2 days, but I had already been sorta limiting carbs or I think it would have been more. Truly, I did feel many of the expected benefits, I felt great on the 2nd day. After I broke the fast, I started eating, 2 days later I had gained back the 3 lbs. Then I dropped 2 lbs the day after haha. So I did lose a little weight I think, but it's very easy to fluctuate. I did feel great, and hopefully I got some of that Autophagy I wanted even though I did have a snack on the first day :). For increased chances of success, I might try not to have so may tasty leftover in the fridge next time! Hopefully soon, maybe in a few weeks I'll try again and try to hit that mythical 3 day fasting mark for max benefits.