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Before anyone breathlessly gushes about their life-changing fasting regime, remember that this study was done on mice.
And for only 24 hours of fasting. I wish we could get more scientific literature on the 16:8 fasting cycle.
Mice have fast metabolism, so 24 hours of fasting for them is more than 24 hours for us.
Now that the 16:8 fasting method is becoming more popular, more research is being done specifically for that regimine.
On more than mice? I'm pretty sure such research has already been done a lot on mice, I've been hearing about positive intermittent fasting / caloric restriction studies for years (but it's always in mouse models).
I wandered into 16:8 as part of general cargo ship steering towards better health/fitness.

Used as just one aspect, along with: going cold turkey on snacking at work, switching to black coffee, and doing some daily simple fitness basics (pushups and the like), and ongoing bike commuting [prior to calorie consumption] the consequences over the last 18 months have been dramatic.

The main reason 16:8 IM helped with significant weight loss for me is certainly the "side effect" of significantly reduced caloric intake (thank you CICO). Normalizing to two meals and much reduced snacking has made a ton of difference.

So much so that when I hit my semi-formal "target" (midpoint of the "normal" BMI weight range for my height) I think I am going to have to get conscious about getting enough healthy calories to maintain muscle etc.

I try to make slightly more sensible choices, and exercise some mediocre "portion" control... but haven't switched diet to speak of.

I am a convert. I can see that it's not magic, but, for me at least IM as part of a broader modest trajectory change is turning out to be honestly life-changing.

I've been doing 16:8 for decades without knowing it was a thing :) For me it basically burns down to skipping breakfast, eating lunch at 12:00 and dinner at 18:00, and that's it.

I did 5:2 for 3-4 years as well, and lost 20kg (~44 freedom units). I did 36 hour fasts, and after a while it just felt naturally, but i'd be lying if i said the fasting days were easy. It gets "easier" but never easy.

I usually took a break from fasting during holidays, and a few years back i never really got back into it, and reverted to my old 16:8 ways. I'd love to see more research on it, but from my own experience, it's nowhere as effective as a regular 5:2 diet.

Not only that, more often than not, it turns out that the original claims turn out to be false or negligible at best.

The latest weight fad was intermittent fasting. Turns out it isn't any better than any other weight loss regime.

https://news.ycombinator.com/item?id=18537250

As the title says, it improves overall health. Nobody mentioned weight loss.

From the article, "...optimal fasting in a timed manner would be strategic to positively affect cellular functions and ultimately benefiting health and protecting against aging-associated diseases."

If you really want to lose weight - stop eating.

I don't know about intermittent fasting, and don't feel like checking your source at the moment. But I know in the case of "low-carb" diets the people publishing research articles on it made up their own definition that has nothing to do with what people actually call "low carb".[1]

So the track record of people who study diets is abysmal in my experience.

[1] https://news.ycombinator.com/item?id=18453665#18457257

The amount of decent studies on actual low-carb diets is near non-existent.
Perhaps the headline should have been "Fasting can improve overall health in mice".
I only have anecdotal evidence but occasional 24 hour fasts seem to reset my appetite in a way that makes me less hungry throughout the day. The easiest way to do it is to start after lunch - and have a late lunch the next day.
Did it affect your sleep? I find that being hungry at night affects my sleep significantly.
The thing with fasting/low-carb is that once you are adapted it takes quite a bit more to "feel hungry". In fact the feeling is qualitatively different.

I eventually tried the low-carb (actual low-carb of <100g carbs/day, not the fake one nutritionists study where "low" is like 40% carbs in your diet) because I kept hearing about it and it was so easy to self-experiment, so why not?

It was like the scales fell from my eyes when I realized that much of what I thought was "hunger" my whole life was actually "addictive cravings" for carbohydrates. And I was really not a fan of grains and sugary stuff to begin with.

There was a really good episode of "Explained" on Netflix that talked about diets. They took a study group, and gave half of them low-carb, and the other half a low-fat diet.

Both groups lost weight equally. They didn't lose weight because of that particular diet, they lost weight because they made better decisions daily, stopped eating out, and stopped buying processed foods.

Just cancelled my netflix this morning when I heard about another rate hike (also hadn't been using it much recently). Can you share what they meant by "low carb", how long the study ran for, and how much weight was lost?

Because I can tell you one thing for sure, the reason I lost weight (and I was only slightly overweight) is because I ate less. And I ate less because I craved less food.

I'm open to the idea this is due to more home cooking rather than low carb per se but I doubt it... I could possibly test this by eating some noodles or homemade pizza or something.

What did the study consider to be "low-carb"?
I don't recall specifically, it was a TV show I watched a few weeks back.

I find your question interesting, though. Why do you not care about what the low-fat diet was as well?

Also, since they lost weight on the low-carb diet, I can only assume that it's one that works!

This was one of the Vox episodes.
How long did it take you to become adapted?
What I described happens after a few days, maybe up to a week for me. Right after getting really thirsty and drinking a crapload of water and pissing it out (I presume this is for hydrolyzing glycogen...) for 1-2 days.

Like I said, I already wasn't a big consumer of carbs/sugar to begin with though.

It took a while for me to start burning fat efficiently when I started keto. YMMV. Day 1 was ok, 2 was difficult, 3 was the worst - had a persistent headache and my mind was at maybe 50% of what it is normally. After that I was fine, except for two issues -

1. I didn't feel hungry anymore, so I didn't want to eat. I had to force myself to eat protein so I wouldn't lose muscle.

2. I couldn't do strenuous exercise for at least a week afterwards. I could walk for several km at a time but running was difficult. Running up stairs even more so. But once I was fully adjusted to the diet 7-10 days in, I could do all of those things.

I'll return to this diet later this year. Really looking forward to it.

This is exactly my experience with the diet.

I've been doing intermittent fasting for about 3 months now. I fast for 16 hours, and have 2 meals a day (lunch at 12PM and dinner at 8PM), I eat 0 to low carbs, since my diet is mostly animal based products (meat and eggs, and I have protein powder from beef and egg which I occasionally take as well).

I really don't feel hungry at all, never. It's insane. I go to the gym at 7AM, after 11 hours of fasting, and I can workout just fine. The difference has been absolutely crazy.

same experience with the difference that I do carb cycle. on workout days I eat high protein,carb and low fat and on workfree days I eat high protein, more fat and few carbs.

workout without breakfest does work, although if I go to very heavy weights, I tend to take a bit of BCAA before the workout.

Yes, it is quite eye-opening.
Not OP, but juicing I had the same kind of problem. It took about three days and I “got over it”. Even giving up alcohol entirely (not that I drank much before hand) made a surprising difference.

It’s surprising how quickly your body adapts to a total change. It’s worth experiencing before you make a decision.

I used to think so as well. I was always of the mindset that I had to feel somewhat full to "relax" me so I can go to sleep. I could never seem to fall asleep while hungry.

But, I found out, it's actually just a mindset thing. Once I realized that, I found that I could go to bed hungry and still get a great nights sleep. I know it sounds incorrect but sometimes attitude and mindset really can influence outcomes.

That's why the placebo effect works.

You can improve quite a lot about your life if you can control your mindset.

But, it's a little more than that for some. Some people are actually able to reduce cortisol in their bodies, regulate temperature, slow the blood pressure and a host of other bodily functions through power of the mind and breathing.
You can start your 24 hour fast after dinner, and skip breakfast and lunch the next day.
I’ve fasted quite a bit, and the first two to five days of any fast your body never wants to go to sleep when you want it to sleep.

It’s been my experience that after seven to ten days fasted, my sleep cycle is basically ‘ideal’ — for me that’s getting tired between 2200 and 0100, and waking up naturally between 0600 and 0830.

I've had exactly the same experience. There's something about going without food for 16 to 22 hours that reduces hunger the following days.
The stomach is capable of stretching and contracting, and eating large meals will tend to increase the expanding capacity of the stomach. Fasting or reducing your intake will tend to quite literally lead to a reduction in total capacity as a result of increased contracture and a sort of “resetting” of your sensitivity to hunger signaling. It’s not really a matter of stretching or shrinking, but altering muscle tone and how your gut reacts to a meal.

Of course you can get the same result by just eating less, but fasting is quicker and more dramatic, not to mention that total abstinence for a short period is easier for some than fine control over a longer period.

(comment deleted)
This might interest some of you - it is a documentary on the same topic - where a doctor goes ahead and explores intermittent fasting for longevity / reducing aging issues. He ends up trying it and becoming a convert.

https://vimeo.com/170735109

This doctor (Dr Berg) also has a channel on the same - and provides some interesting easy to understand scientific explanations on different intermittent fasting related items. I remember the explanations on the body need for potassium was interesting.

https://www.youtube.com/channel/UC3w193M5tYPJqF0Hi-7U-2g

A little more info on Dr Berg: he's a chiropractor doctor not a medically trained doctor. He has a lot of good information, but it's also wise to verify any of his info from other sources.
It's wise just to disregard anything and everything he says.
Unhelpful and mean-spirited. Not a comment worth posting on hacker news.
Needs appropriate quotes

> he's a chiropractor "doctor"

well..most doctors( without quotes) i've been to know nothing about diet and nutrition.
It's interesting but without large, long term longitudinal studies making health claims is shaky at best.

It might improve specific health parameters but whether those improvements translate into a longer and/or healthier life can't be assumed.

If you've never explored fasting for a couple days as an adult, it's definitely worth the experience.

Once the body gets into the fat-burning mode and all the pangs of hunger and mild headaches vanish, everything changes and it's like you can go climb a mountain with nothing but water.

Those familiar with atkins/ketogenic diets will have already learned this stuff about themselves. But it's interesting to note that the same operating mode is available without any food at all.

Even if you don't embrace fasting as some kind of healthy practice, being aware that; no, you're not actually starving when you're hungry because you haven't eaten carbs for a few hours, seems like a useful fact to internalize. As long as there's fat on your person, you're not starving, just stop eating long enough to give your body a chance to switch fuel sources.

It's actually a quite different experience to run off fat, the headspace is changed, there's a mental clarity and physical lightness and agility (you're empty). I find it quite pleasant, especially for physical activity.

>> "The research was conducted using mice, which were subjected to 24-hour periods of fasting."

Nobody fasts for 24 hours. This study lacks to mention if say same affects were observed based on shorter amount of fasting time.

A lot of people fast for 24 hours. I do it once a month. Where did you come up with the ridiculous assertion that nobody fasts for 24 hours?
maybe he meant 24 hours hardly qualify as fasting, if you don't eat breakfast, that's just skipping one dish

i am usually doing 36 hours starting after dinner until next day after breakfast and it's way too easy, even 48 hours would not be problem. the issue for me it's i am cooking for family and children sometimes don't finish their stuff so it's difficult to combine it with my fasting, if i would be single i would be doing 48 hours regularly

I do, once a week I do dry fasting and it's a miracle !
When I tried fasting I did 36 hours every other day for two months.
That's what I've been doing for years
Interesting... I take my initial comment back.I wasn't aware that people actually abstain from eating for long periods of time (+24 hours).
I don't do it often/regularly, or schedule/track it, but if I get to the end of the day and don't feel particularly hungry, I don't eat. Since I usually only eat in the evenings anyways, I guess skipping one evening would put me in the 42-48 hour range.

If I don't feel weak, irritable, or hungry the next evening, I'll go another day. Without records, I'd guess I skip two consecutive evenings once or twice a year, and skip a single evening a few more times.

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I've been doing 23 hour (dinner-to-dinner) fasts twice a week (not back to back days) for nearly 6 years. It's the easiest form of weight control I've come across. It's nice to see it may extend my longevity as well. Anyone wanting to try it just know the first 2-3 times are the most difficult. It does get much easier after that. I've had blood levels checked and it stunned my doctor. He said my LDL is at the level of child under 10 years old. If anyone has questions about 23 hour fasts I'll gladly answer them.
Whats your weekly protocol?
Monday night after dinner I only drink water until bed. Tuesday I only drink water and black coffee until dinner time. I do this twice a week. Fasting is flexible. You can do it whatever times or days you like. I prefer to fast beginning at night because I sleep through the first part and I've never been a big breakfast person. I pretty much never eat breakfast. Always been a big dinner person so it works well for me.
Do you have keto breath on whole of Tuesday? I work with people and probably can’t do this.. but very interested.
Never heard the term "keto breath" before. Haha. Yes but the more water I drink the better the keto breath. It does seem like it would be difficult to do but I was very surprised how much my hunger levels went down.
how are your energy levels on the fasting days?

I presume you load with water to help distract from the hunger?

I drink at least a liter of water to help keep the feeling of hunger away. I learned that if I keep the meal small preceding the fast I don't struggle during the fasting day. Sometimes even if I follow all these rules I may feel hunger regardless after hour 21.

I'm not the best person to ask about energy levels because I take a medication that depletes my energy so I'm drinking caffeine a lot to stay energized. I can honestly say the last hour is the real challenge after doing it this long.

This is anecdotal, but I've typically fasted in a similar way (eat between 4-8pm only) for around 5 years. A few years ago I was running 20-30km while fasted without issues. I was running slow (5:30 per kilometer) but I felt pretty good, with steady energy and no weakness or crashing. I took a while to adapt to not eating first, but I'd say it was a matter of a month at most.

I personally did (and do) drink a lot of water if I feel hungry. I usually end up hungry the next day if I allow myself to eat past 8 or so - it's always a mistake for me to do that.

I allow myself to have tea and coffee, which some people say isn't true fasting because you have to metabolize the things in the tea or coffee. I don't mind. I'm doing this to maintain control over bad eating habits which lead me to be very overweight. I have ADHD and I suppose it comes with poor impulse control in my case - I tend to be very "all or nothing", so fasting works very well for me. I have nothing until I can have it all :)

I just hit day 7 of my current fast. I’ve also completed a 60 day fast which was quite strict, as I didn’t allow myself tea or coffee.

If anyone is interested in more details, let me know and I’ll do my best to answer any questions.

Which supplements did you take, and what was the goal?

Have only done 72 hour fasts, but allow myself both black coffee and zero calorie soft drinks.

I did water/salt only for the first 30 days and added in more supplements for the last 30 days. Super strict no coffee/tea/or flavored anything even if it was calorie free.

If you shoot me an email, my username at gmail, I’d be happy to share my spreadsheet and before/after photos. Goes for anyone coming across this in the future.

I've been doing intermittent fasting for about a year now in combination of lifting weights, training mma and bjj and I'd say that it would be very hard for me to go back to a "normal" eating pattern. I've always been in good shape before starting intermittent fasting but the difference is huge. Not only have I decreased my fat precentage but I've also gained muscle mass.

I don't feel hungry even when I'm fasting, I sleep better, and I don't crave for fast food, snacks etc anymore what so ever. On top of that I also save a lot of time that I used to spend eating 6-8 meals a day.

This is my new normal.

i don't believe you.
So as another anecdote to add to your data points: I've been doing intermittent fasting more or less for 2 years, eating latest at 8pm and only breaking the fast by lunch time (around noon - 1pm). That gives me, usually, a 7-8 hours feeding period while fasting for 16.

I don't feel hunger at all when I wake up, I drink a glass of water in the morning and then a coffee in the office. Alas, I don't feel hunger as I used to, it's not a craving, I don't feel like "I need to eat now", it's a much more manageable feeling.

And I go to the gym in the morning fasted, it works really well for me. The only times I feel it's harder to have energy is when I'm cutting down weight (and eating with a 700 kcal deficit).

i am usually doing 36 hours starting after dinner until next day after breakfast and it's way too easy, even 48 hours would not be problem. the issue for me it's i am cooking for family and children sometimes don't finish their stuff so it's difficult to combine it with my fasting, if i would be single i would be doing 48 hours regularly

little bit crisis it's around 24 hours, then even next day morning around 36 hours it's fine bit i guess around 45-48 hours would come another crisis