> I find the 16/8 routine tends to work best for me personally

That timeline as "fasting" is funny to me up because that is basically how people used to eat in 20th century USA, pre-obesity. You'd eat three meals a day, all reasonably sized (or even small by todays standards), and at specific times. No you can't have a snack, that would ruin your appetite!

But now people are addicted to food and abuse it rampantly as is evidenced by the majorities waistlines and health care expenditure, it's terrible for us all but it's not only the most culturally acceptable form of substance abuse, it's widely encouraged and even celebrated. Strange times.

Do you find that you're able to do cognitively demanding tasks while fasting?

Even small fasts seem to sap my concentration and critical thinking. Once I eat again I feel like I think better.

Mental clarity is a challenge when fasting on an otherwise stereotypical American diet... those blood glucose swings are no joke.

However I have no problems on keto, or even just a consistently low-GI low-carb diet. If anything, fasting seems to improve my discipline and "depth-first" thinking.

Interesting. I did an "animal-product only" diet for about six months, and I began to feel sorry for everyone else and their inability to think deeply. I was in an almost constant state of enlightenment. Then my buds convinced me to go on a 2000 mile road trip, and after the first stop at Wendy's I lost it, and haven't had the will to go back. It's been like 4 years now.

Can you elaborate on what you ate? Curious.

animal-product only ? No veggies?

Correct. I even ate organ meats as a source of vitamins and minerals I thought I lacked.

“KetoAF” for a search term.

> Do you find that you're able to do cognitively demanding tasks while fasting?

Absolutely.

> Even small fasts seem to sap my concentration and critical thinking. Once I eat again I feel like I think better.

That's kind of normal when you start with (intermittent) fasting, may take at least some days until it gets better. Especially if are on a high carb diet and already developed some degree of insulin resistance your body is unable to fully switch into fat burning mode while the glucose stores are already depleted. This results in low energy and food carvings. Once that is regulated well your mental abilities likely won't suffer.

I do multi day fasts (water Ott broth fasts, so no carbs) and once I am in ketosis I actually feel like I can concentrate as well as when I eat.

It's key to not refeed carbs at all during fasting (no juices, honey, etc).

I also occasionally do keto between the fasts which might have helped my metabolism switching to ketosis more quickly.

Ketosis is - in brief - a metabolic state where the body primarily used fats to burn for energy. Our bodies are perfectly suited to operate on ketosis. But this is only reached if glycogens are completely burned which means to u need to avoid refeeding carbs entirely.

Basically it is simpler to eat nothing at all, than to eat at a caloric deficit.

Think of it this way: our bodies have evolutionarily adapted to be able to live off our fat reserves (when overweight).

I recommend reading material or watching videos of Dr. Jason Fung, a Canadian nephrologist who makes compelling well-sourced arguments and explanations.

What is "water Ott broth"? Couldn't find it in Google.

"water or broth"

This

You could switch your metabolism to ketosis, then your energy level won't depend on blood sugar and will be more consistent through the day. I do my most cognitively demanding work without food.

There is a hump for me around 12-14 hours where I do feel distracted by the urge to eat. Once I make it past that I find that I have more mental clarity than before the fast.

> Do you find that you're able to do cognitively demanding tasks while fasting?

I'm only speaking of IF, but yes. Multi-day fasts may be different, but I actually think best right after my workout during my IF window.

The effects are so pronounced I'm considering just eating a single meal each day right before bed.

I've done intermittent fasting both on a fat-based diet and on a carbs based-diet.

On a carbs based diet, it feels like there's an animal inside me craving for food all the time. Then I feel drowsy and sleepy if I don't eat anything for even a few hours. As a developer, that's terrible. I feel really bad.

On a fat-based diet (e.g less than 40g of carbs/day), I feel absolutely great, and I don't feel hunger. When lunch comes, I feel just empty, but no craving at all, no hunger. Then the fasting becomes easy.

The caveat: switching from carbs to fat is not pleasant, takes a few days and isn't any fun. If you break it with a piece of cake, then you'll have to make the switch all over again and it won't be pleasant again.

On the rare occasion I have fasted for a couple of days, I noticed I was more focused not less. Physical exercise I would not recommend though.

It depends... I would not do an intense weight lift or 1h run but you can definitely go for a fast walk or 20 minutes moderate run.

This is likely just a function of fluctuating glucose levels. Fasting + becoming fat-adapted can help with this.

That said, I have gone through fasts and said f-it at hour-mark 34 because I was on a deadline.

It's not a religion, so do what works for you - but I would at least try it.

I want to know the relative benefits of the different protocols (I asked on the fasting subreddit, but didn't get much response).

I am not overweight, but I see that IF can increase growth hormone and testosterone, and increase insulin sensitivity, which are of interest to me. I would like to know if I am better doing a couple of longer fasts peer week, or if skipping breakfast would be enough. (Longer fasts feel like they have more benefit, but are more effort, especially when I am trying NOT to loose weight).

Does anyone know of anywhere good to compare the benefits of different IF protocols?

How do you maintain energy levels through a 36 hour fast?

Edit: Thanks all! This’ll help me progress from 16/8 to consistent longer fasts.

I am relatively adapted to it at this point, so it doesn't bother me as much.

I time it so I start the fast towards the evening and then it ends mid-morning - so you're only really pushing through one full day without food.

I'll have coffee/tea for caffeine and electrolytes seem to help depending on your situation.

Start with several smaller fasts before going full 36 and if you need to eat before the full 36 hours are up, don't kill yourself.

The biggest realization is just coming to terms with how much what a lot of people think of as "hunger" is often just boredom or cravings and not actual hunger. That was eye-opening.

Do you break fast eating specific things or just go about eating your usual meal?

I typically don't eat breakfast. I eat a relatively low-carb diet throughout the day w/ more carbohydrates around my workout (in the evening)

While I haven't done 36, 24 is relatively easy. The idea that your body needs constant food intake is a modern myth. It's mostly your mind that's been programmed to want to eat that often. Also, once you eat the insulin spike triggers the next wave of craving, and so on. Fasting is not the same because you're well, um, fasting.

Also, if you avoid sugar for a week before fasting that helps a lot, or rather, I should say that it helps me. Eating sugar messes up my ability to know if I am really hungry or if it is just too many Candida bacteria in my system messing with my brain chemistry.

Anyway, if you like, try avoiding sugar leading up to avoiding fasting.

I would say that avoiding sugar as much as possible in general is a positive. Avoiding unnecessary insulin spikes is a positive.

> The idea that your body needs constant food intake is a modern myth.

Modern food intake also trains the digestive tract (most notably stomach) to never be empty, and we end up confusing signals of hunger with an empty stomach.

I heard that Japanese (or was it China? Korea?) people have this rule of thumb of eating only up to ~80% of stomach volume; no idea if it’s factually true but having this rule of thumb of not filling myself to the brim as we seem to culturally do currently seems to be extremely positive I’m my experience.

Letting go the social baggage of “bon vivant” and “oh my god I’m so full this was soooo good” seems to be just as hard as not smoking when many around are smoking.

“one should eat to live, and not live to eat” says Molière, but even being acutely aware of that, I struggle to fight the deeply ingrained social pressure, as even most foodies/fasters I know seem to subscribe to this “all you can eat” way of life (although with healthy food)

Goddamit when I was feeling great, all sporty and fit (athletic even, dare I say) everyone was saying I was too thin, and now that I feel like shit having some 10+kg excessive weight to shed, everyone around says there’s no need to, and worry a lot when I don’t take a second or third serving.

>I heard that Japanese (or was it China? Korea?) people have this rule of thumb of eating only up to ~80% of stomach volume; no idea if it’s factually true but having this rule of thumb of not filling myself to the brim as we seem to culturally do currently seems to be extremely positive I’m my experience.

The traditional Buddhist notion is that one should eat to the point where one more mouthfull would fully satisfy oneself.

In the West we've turned food into a source of pleasure. We no longer see it as a source of nourishment, and the foundation of our health, but as an entitlement to tongue orgasms.

Fasting helps to change our relationship with food. It's about proactive control and not succoming to the minor inconvenience of feeling a bit hungry.

I do. But as Soylent would demonstrate some people aren't interested in food as a source of pleasure.

I have been on IF for almost three years and started recently on 36 hours once every three weeks. If you can do 24, 36 is not too much of a problem. My last 12 hours of the 36 hours is sleeping, so I don't think about food or feel hungry when I am sleeping. Also, I ended up doing it for 38-40 even though my intention was to do it for 36 hours because of my sleep.

Build up to it from shorter fasts. Pay close attention to caloric intake, it's easy to undereat when fasting. Eventually you will be unable to not maintain energy levels though the fast.

I have done a couple 36 hour fasts. What broke me was hunger, not low energy. Didn't feel any less energized than usual, really. But resisting the urge to eat after you've been hungry all day and someone puts a meal in front of you is hard.

in many people’s experience (mine included) there’s phase change sometime in the 48-72 hour mark in which hunger/appetite essentially disappears (some describe it is gone, some as easily ignored background noise)

Personally, I’ve gone more than 14 days several times, I usually start when not feeling very well (and lacking appetite) which makes even the first couple of days trivial.

If you do want to go farther than 36 (at your own risk of course - I am not a medical professional and this is not medical advice) make sure you are well vitamined, well hydrated, and well electrolyted (e.g. with snake juice) - very often, need for some essential vitamin/mineral masquerades as hunger or appetite.

To underline this. People have died starting eating after a long fast. While the risks are probably manageable, and other people have successfully been fasting a full year, do educate yourself on Refeeding syndrome before doing any extended fasts.

https://en.m.wikipedia.org/wiki/Refeeding_syndrome

> more than 14 days several times

Isn't that how anorexics end up unable to eat at all, though? They go so long without eating that the "good" bacteria that permits digestion disappear so they're no longer able to process food.

I am not familiar with the process anorexics go through, but it is likely very different - thousands, possibly hundreds of thousands, do fasting of 2-7 days on a regular basis with no ill effect (on the contrary - often with good effect).

Good bacteria can likely be reinstated by the body itself (the appendix is a cache for them), from food, or if all else fails - by FMT. I’m not an expert on this, and may be wrong, but from a lot of reading - any anorexia symptoms and processes seem to be entirely absent from mindful fasting.