[TimSchumann]

I really think a 7 day fast should be 'mandatory reading' as far as life experience goes. You learn a lot about yourself.

Also echo the mental clarity side of fasting. The weight loss was great, but how I felt was even better.

The crazy thing is, if you can get to 7 days, anything past that is just mental and you can go as long as you have the body fat to sustain the fast, provided you're keeping an eye on your electrolytes and not drinking too much water.

[egeozcan]

I'm not sure if starting something like a 7-day fast without medical supervision is a good idea, and I'm also not sure if any medical professional would allow you to do that, just thinking out loud.

Don't you think it's too dangerous to name it essential life experience and recommend it to random people on the internet?

I'm really asking, I'm not knowledgeable about this at all, and my questions stem from pure gut feeling.

[TimSchumann]

I feel 100% confident, based on my experience, in saying that almost any healthy adult has the ability to fast for 7 days without any negative consequences to their short term or long term health. In fact, I'd say there's only positives.

Obviously if you feel differently, talk with your doctor. I am not a doctor, and this is not medical advice. I thought that went without saying on the internet, but just to be extra careful, there it is.

Couple of caveats in the almost. Pregnancy, Eating Disorders, Elite Athletes functioning at under 5% bodyfat, and again the key word being _healthy_ here. If you have any kind of condition, disorder, disease, etc. obviously talk to a medical professional.

Most people just don't have the desire to do it, and if you're not used to fasting and eating a standard diet, the first few days will make you feel terrible both physically and mentally. Just like anything, it gets easier with practice.

[wutbrodo]

> If you have any kind of condition, disorder, disease, etc. obviously talk to a medical professional.

That's sort of the rub in cavalierly recommending things to the general population, even when they're only somewhat extreme. There are plenty of undiagnosed conditions out there, and the further you move from the center of the distribution, the more you're going to sweep up potential risk in ways that aren't easily caught with a simple "not applicable if".

I say this as someone who fasts pretty often, though usually not more than 2 days. It's the same reason I wouldn't recommend everyone go out and take 200 mcg of LSD, "unless you have a mental health condition". This world of perfect information about one's own health that you're imagining simply doesn't exist. (Again, I say this as someone who thinks LSD is wonderful and salutary and has recommended it to many many friends in person with the appropriate personalized caveats).

[milchek]

I also question if 7 days is safe for most. I don't recall exactly when and a quick search now yields a lot of random gimmicky fasting product sales sites with blog posts written to generate traffic that aren't scientific enough, but I do recall that there is a point (after 72 hours?) where your body starts breaking down muscle and that prolonged fasting is dangerous as your organs get hit next?

Perhaps someone here with medical experience can chime in, but I agree 7 days seems a bit extreme for most people.

[rhinoceraptor]

I haven't seen any convincing evidence that significant muscle loss occurs with a 7 day fast. If you get a DEXA scan before and after, you will have lost a lot of "lean body mass" and your muscles will be smaller, but it's only because you lose about 5-10lbs of water weight.

The only major health risk is refeeding syndrome, and even then it's only really notable if you're an alcoholic or have anorexia. If you're otherwise healthy with normal sodium/potassium/etc. intake and you take it slow when refeeding, I don't think it's particularly dangerous. Obviously, talk to your doctor, and it's probably good to get blood work before doing something like this.

[TimSchumann]

I lost zero noticeable lean muscle mass on my 60 day fast, at least no more than I would have sitting on the couch doing nothing.

There's just not a metabolic pathway for breaking down muscle/organ tissue for energy when you have adequate fat stores. We would have died off as a species a long time ago if that were the case.

In the grand scheme of things, if you have the body fat, 7 days is nothing for a fast.

Edit: To those asking, yes. I fasted for 60 days, water and electrolytes, no calories.

[CamelRocketFish]

When you say 60 day fast, are you saying you didn’t eat for 60 days and just drank water?

[brodouevencode]

https://news.ycombinator.com/item?id=27619297

I remember his post from a few months back - found it rather inspiring.

[CamelRocketFish]

Thanks a lot for linking that @brodouevencode

[pid-1]

Did you exercise or work during this period?

[TimSchumann]

Once-ish a week there was Light lifting, think moving a whole trees worth of firewood or a light day on a family farm.

Quite frequently I hit over 10k steps/day on my step tracker, sometimes double that. I live in the middle of a major city and walk everywhere, and this was before work from home.

If you’re looking for exercise/fasting advice check out my fat per unit time post elsewhere in this thread.

[sedivy94]

Thought experiment...

Humans have weathered long durations of food insecurity for much of their existence. If the default metabolic solution to fasting was harvesting energy from skeletal muscle and smooth muscle... well that strategy wouldn't work for very long, would it? The lowest hanging fruit is muscle/liver glycogen, and fat mass after that.

Breaking down proteins (gluconeogenesis) is a metabolically expensive process, requiring large energy input for low energy output. The body is wholly invested in protecting these vital organs. Skeletal muscle has a reputation for being fickle, subject to change based on stimulus and energy demands, but those adjustments are most significant and relevant to those who are invested in maximizing lean mass (athletes, bodybuilders, statistical outliers).

Fasting is relatively protein-sparing, all things considered. The observations of apparent muscle loss can be attributed to loss of muscle turgidity - a reduction in glycogen, intracellular fluid, and electrolytes. The difference between fed and fasted states, both visual and internal perceptions, are quite extreme.

Are extended fasts ideal, or even generally recommended, for someone with the singular goal of building muscle? Absolutely not. But it is a flexible tool when goals shift towards catabolic outcomes (losing weight). Furthermore, the downstream benefits of fasting can translate to improvements in insulin sensitivity, nutrient partitioning, muscle-building, and body composition... which are relevant to anabolic outcomes.

[SapporoChris]

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2495396/

"A 27-year-old male patient fasted under supervision for 382 days and has subsequently maintained his normal weight."

By comparison 7 days is trivial. More to the point, a 7 day fast with medical supervision should be safe, if it is not, the supervisor will advise against it.

[femiagbabiaka]

Not to be snarky, but reading the linked study would be helpful here. Your body is quite intelligent when it comes to drawing on its energy reserves.

[brodouevencode]

This is a damned-if-you-do-damned-if-you-dont situation. If OP says you should fast and someone gets hurt, that's bad. If OP says you shouldn't fast then what gains could have been made in that lost time.

A better way of looking at it is to take it incrementally

* skipping breakfast

* skipping breakfast and lunch

* skipping a whole day

* eating one meal every two days

* eating one meal every three days

* ...you get the point...

I don't think OP would advocate just jumping right into it. Start small, work up from there, listen to your body. You wouldn't jump right into running a full marathon.

[TimSchumann]

Exactly right, to all of this advice.

I believe I say multiple times in this thread nobody should just jump in and do 60 days, however I believe anyone (caveat-ed up thread) can 'jump in' and do 7 days at any point in their life.

It won't be easy, it'll be especially hard if you've never fasted before and are on a standard diet, but it won't be dangerous. It'll just probably be the most difficult physical and mental thing you've ever done.

Also, thanks for linking to my spreadsheet up there.

[lm28469]

> I'm not sure if starting something like a 7-day fast without medical supervision is a good idea

I'm not sure starting a western diet without medical supervision is a better idea given 75% of the west is overweight or obese. Unless you have medical conditions a 7 days fast is a walk in the park in term of health

[m348e912]

You bring up some interesting points. I've dabbled with fasting in the past and it seems to be relatively safe and beneficial up to 10 days but there are two mistakes I see people make.

Mistake 1: Drinking pure water. Your body does need some specific minerals even when fasting. Cole Robinson, a fasting focused youtuber (who is not for everyone), has shared a Magnesium, Sodium, Potassium, Sodium Bicarbonate & Water recipe he calls Snake Juice that keeps electrolytes steady during a fast.

Mistake 2: Drinking liquids that break the fast. I've watched youtube videos of fasters add things like diet soda, gatorade, and even jello to their fast. That defeats the whole purpose and negates any positive effect.

[godshatter]

Diet sodas get a bad rap and for good reason, but I've been unable to stick with anything other than diet soda long term (though I've tried multiple times). I know that diet sodas can spike blood sugar in some people, but it doesn't break me out of ketosis when fasting. YMMV.

[m348e912]

Just my perspective, but I think diet soda certainly breaks a fast. I can see how it could potentially not affect ketosis, but as far as fasting goes, water & minerals are truly the way to go. I will also concede a true "water" fast makes the fast much harder, although I think that's part of the experience. It's not supposed to be easy.

[HanMei_333]

> The crazy thing is, if you can get to 7 days, anything past that is just mental and you can go as long as you have the body fat to sustain the fast,

It's not that easy. You have to properly substitute electrolytes - sodium, potassium and magnesium. And that is almost impossible without small doses of carbs.

My longest fasting was 42 days. I did 28 days three times before. I'm fasting more or less regularly (once per year) for about 25 years.

Don't do very long fasting without guidance of a doctor. Your heart needs properly balanced electrolytes.

EDIT: I've just seen your other comments here also underlining the need of electrolytes. I still leave my comment here for the other readers ...

[michaelbrave]

I would say there are some things to watch for if doing long term fasts, one is salt and potassium levels to prevent heart attacks, especailly true for those of us who are on the larger side, and especially as one get's closer to say the 20 day mark. A week or two probably wouldn't kill anyone if they have the fat stores, but a heart attack prompted by lack of salts is a potential concern.