> Adult hippocampal neurogenesis is a process that describes the generation of new functional DGCs from adult neural stem cells through the amplification of intermediate progenitors and neuroblasts, as well as the integration of these new neurons into the existing neural circuits.
Will my values change in ways that they are unlikely to change without the changes to my brain? By analogy, drinking alcohol has temporarily affects on my judgement because it affects my brain chemistry and on the whole it makes my judgement worse (although sometimes it has removed unhelpful inhibitions).
To me the premise that the possibility of changing my brain through fasting is unquestionably a silver bullet free of tradeoffs is suspect. Or to put it another way, the fact that fasting had a particular effect does not imply that effect is a positive one.
Furthermore, hunger is a strong motivation toward behaviors that are ethically suspect in its absence. A full belly is a rung up Maslow’s hierarchy.
People who spend their days starving mice at scale have incentives to interpret that starvation in positive ways. It would be hard to rationalize starvation and vivisection otherwise and still consider one’s life choice reasonable and ethical. Hence, I am skeptical of acting in the ways an optimistic interpretation of the report suggests. YMMV.
I don't think that we need to apply a value to neurogenesis and I do not think the authors do either except that it seems to be correlated with other quote good behaviors like exercise.
Presumably neurogenesis is occurring all the time and is restricted to a small set of regions in the brain and the new neurons form in just those very strict set of regions. Those neurons are not moving to the neocortex, just a few millimeters within the dentate gyrus. That is to say even robust neurogenesis is not likely to change your mind, cognitive experience, personality or intelligence in any measurable way.
I think the primary "function" attributed to adult hippocampal neurogenesis is improved memory.
But the parent comment is unfair insofar as scientists don't randomly chose to food deprive or "vivisect" animals because they think it's intrinsically fun. Running these experiments requires a huge amount of annoying busy work that I can't imagine anyone choosing to do without being paid or having some other motive.
In particular, the reason intermittent fasting is studied is because there's a large and increasing body of research that suggests that it may be of benefit to a wide variety of health measures.
Sorry for not being clear. I don’t think people starve and vivisect mice for fun. And I agree that there being money in it is much of the moment to moment motivation for the moment by moment steps that are necessary for it to happen. Putting a happy p-hacked face on the process is how ordinary people rationalize what they are doing as something other than what it is.
The business of cutting apart animals and looking at the insides claim revealed knowledge isn’t new. The Romans called it “haruspicy” and also built wealthy bureaucratic institutions in service of narratives useful to the powerful.
Contemporary interest in fasting research is helpful to those who find advantage in moralizing upon obesity. Intermittent fasting is a virtue reserved for those with food security. It’s attractive to people whose socio-economic status insures that going hungry is a choice and a display of will power. Not weakness. The conclusion that it makes such people smarter is self serving.
The preponderance of health evidence is that starvation is detrimental to human health and creates long term cognitive problems. But lab mice are an industrial product and labs are industrial institutions and the money keeps flowing so long as the results are acceptable to those providing it. That’s the way it has been for millennia.
I worked in a neurogenesis lab for three years, so my attempt:
The cells in our body are continuously replaced throughout our life, with the exception of our brain cells. For many many years we believed that mammals didn't create new brains cells in adulthood. You were born, your brain grew and developed as you became an adult, and then you were done.
About 20 years ago we realized that that was mostly true, but small parts of the brain continued to produce neurons through adulthood. This happens in two important parts of the brain:
- the hippocampus, which is associated with memory
- the olfactory bulb, which is associated with sense of smell (and memories related to it).
Humans have a relatively weak sense of smell, and if we create new neurons in the olfactory bulb it's much less than other mammals.
The process is convoluted, but small regions of the brain create those new neurons and they migrate through fluid-filled holes in your brain - most die, but a small % survive and incorporate themselves into that brain structure. The key thing to realize is that neurogenesis accounts for a tiny fraction of the neurons in our brain, and yet it's still an important process.
So why does adult neurogenesis matter, and what does it do for us? Neurogenesis is tied to our ability to learn and form new memories. So, if it's impaired, our ability to learn is reduced. There are tons of things that impact it - age, sleep levels, exercise, among others.
In the lab I worked at, we used to induce a form of brain damage to rats which greatly impaired neurogenesis, then run them through mazes, which they did quite poorly at.
We took some of those same brain-damaged rats and had them run in exercise wheels for two weeks, and they were suddenly doing just fine at maze tasks. When we stained and looked at their brain, their neurogenesis rate was back up to (or even above) normal levels.
We've known for a long time that exercise is great for your health, and there's a growing body of evidence that the same is true for intermittent fasting. What's interesting is that it's not just good for your overall body health, but both can help keep your brain working optimally by increasing neurogenesis and BDNF (which protects your existing neurons).
It's worth noting that there's some controversy about the extent of adult neurogenesis in humans. If it exists it's likely at the scale of a few neurons per day. Whether or not that means that increasing it by fasting is important is unclear.
Yeah, a 2018 UCSF study was unable to find any adult neurogenesis in humans, so it's still a controversial subject when it comes to humans.
Even if we had confidence that adult neurogenesis occurs in humans, we can't really expose humans to a stimuli, kill them and then do a BrdU stain, so it's difficult to know how well any rat study translates over to humans.
The early evidence in humans was based on radioisotopes present in the atmosphere after atomic tests. You could diffentiate neurons in people's brains (after they died) if they had been born before the 1940s.
I feel like the term intermittent fasting is used by many folks to mean different things. It would be nice if there were more precise terminology here so we could communicate more clearly.
I'm very skeptical of any diet related advice based on studying mice. Mouse metabolism is very different from human metabolism.. Fasting a mouse for 24 hours will result in a fairly large loss of body mass. Fasting a person for 24 hours will result in a pound or two of weight loss.
I'm not against doing these kinds of studies on mice but the only conclusion you can really get is that we should do longer studies on animals that are closer to humans or on humans themselves.
Pound of fat, or, in SI, 453 grams of fat, is 4077 calories (9 calories per gram of fat).
Most probably, weight loss will be less than pound in water calorie restriction.
Also, there was studies on Ramadan fasting and they've found almost two fold increase of serum brain-derived neurotrophic factor at the end of fast. Level of BDNF correlates with neuroneogenesis in brain.
Stay up all night playing factorio. No food, of course, because you're in a middle of a refactor and you can't be bothered to eat. Crash in the afternoon and sleep until midnight. There you go, easy mode health++, apparently.
This is for mice, but if done fastidiously cancelling boozing at night and if a caffeine addict changing to black no sugar/diet soda and stopping all night time snacking is not tiny. Losing external nighttime calorific activities might not be great for mental health though.
Generally for health you aim for a longer fast with perhaps social break nights. But whatever works.
From everything I've read, it is on a spectrum. 12 is on the spectrum, but supposedly the longer the period the more marked the effects. I'm not sure at what point the curve flattens and drops off.
12 is better than, say, 8 or 6 (e.g., snacking at night).
Curious how your experience compares to your pre-IF state 5+yrs ago?
There's a point it becomes destructive. I tend to ignore hunger, and I find after 20 hours or so my mood nosedives, I get shaky, generally things go south quickly and even if I eat I'm still a wreck for a while. 12-16hrs is probably the sweet spot from my experience.
Your IF experience sounds hard, is IF worth it for you?
Would you mind sharing your BMI from before IF? Also curious if you feel IF is better than the alternatives (e.g., Keto, which for me has been the "easiest" of the effective diets)
Oh IF is just how I have generally lived my life, long before it was "a thing". So not much to compare.
I did have a really good experience doing long fasted running in the morning. At first I couldn't go three miles without breakfast. But eventually I could do twelve straight out of bed and feel great.
As I understand, fasting trains your body to supply blood glucose from fat stores, which breaks your brain's craving for sugary foods- which are a crutch for getting your blood sugar up. (Remember, your brain runs mainly on blood glucose)
Keto does the same thing a different way. But to me IF is way easier and healthier. (I strive to eat a Mediterranean style diet which ain't Keto!)
I would say the experience for me is really good- as long as I avoid the cliff, which is what I was warning about. Basically, just don't try to get all extreme thinking longer fasts are always better.
Most people (especially those who have built up some "reserves") can survive for a long time without food and would safely last months on just liquid. (treated water or herbal tea + some vitamins & minerals).
The mental benefits in terms of ability to concentrate are hard to put into words. It's different than with micro-dosing which gives you a false sense of your abilities. The long fast showed me what kind of energy gets unlocked when we feel like we're close to snuffing it. It's like the body gets ready for a final push so that you can hunt and find food. I stopped doing these crazy type of diets after discovering IF.
IF gives me a similar result (the highs and lows on the graph are less extreme but at least it's sustainable) without landing myself in hospital (in retrospect the kidney stones were most likely legacy/cruft that needed to be refactored anyway, and who knows what kind of cancers or other long term illnesses my body "ate" while I pushed him that hard). I understand this is all pretty mental to read but back in 2013 there was no IF and all I had was the theory that dogs and rats that were kept on an IF survived longer.
!!!
Disclaimer: this is the most extreme one I ever done so please don't start out with this if you want to try... try 7 days or 2 weeks are enough time to do some extreme diet. But don't go overboard - which is way too easy after 2 weeks because you'll be so high on your own achievement and you won't feel hunger. It'll feel like you're able to continue for 2 or 3 months. (you won't). the key is in recognizing this and to quit regardless! Also knowing your own body is key. E.g. if you do sports and have a 20 year history of pushing yourself to extremes probably yes. But I understand why doctors bail and give the "blanket advise" that this is irresponsible.
- It is not stated if the diets are isocaloric or hypocaloric; probably because it wasn't measured. Timing restrictions and calorie restrictions are two different stressors on the body, and all else being equal stress is positively correlated with neurodegenerative effects. It might as well be only isocaloric intermittent fasting is indicative of BDNF increase and hippocampal neurogenesis.
- Fasting time is a very specific slice of the circadian rhythm; between 15:00–07:00, so this study is only skipping dinner and not breakfast. This is important because body has different stress responses early in the morning (we wake up with higher cortisol levels) and our insulin mechanism also reacts differently to food deprivation based on time of the day.
- Limits of animal models already mentioned, and I think it is particularly compounded around the concerns around timing and bioeconomics of growing brain regions. Mice and humans have similar encephalization quotients, but size of neural cells are constant between both, so is the cost to create or upkeep them. Same concern goes for the number of days of energy each animals bodies can store. So the underlying calculus to make new brain cells or not might be vastly different. For example maybe humans need to undergo a much longer (e.g. multiday) fast before this effect kicks in.
Also, is the diversity of metabolism found in humans taken into account? Some humans are 50kg, others are 100kg. Some are naturally skinnier, some are fatter. Surely it must have an impact on fasting rythmes too.
Every time I see a research being published on HN, it ends up being a mouse model. Is there a place on the internet where I can see a list of publications describing the final (or close to final) stage of a research made on humans? Mouse model researches worsen my overall abstraction of where the humanity, in a scientific sense, is.
I often read these threads about fasting/intermittent fasting on HN and see a lot of nitpicking about flaws in the study.
Given that almost all studies tend to fall between "no effect" or "clear positive effect" of fasting on health, do we have enough evidence to say "fasting is good for your health?" I still believe there's value in further research to nail down exactly how and how much, but curious if we can make the overall statement confidently.
If you can successfully pull it off, there's substantial evidence it is generally beneficial. But I have a genetic disorder that impairs fat processing (so I had no real fat stores to draw on while fasting) and I began fasting or semi fasting while homeless at times when I was too broke to afford food.
Initially, it was extremely hard on me. I routinely threw up on fasting days and usually managed to get something into me so was really only light rationed, not actually fasting. It took years for me to get well enough for fasting to stop being horrible torturous drama and I still have extremely severe diarrhea when I resume eating.
Second, there is a thing called Refeeding Syndrome that can occur when you break a fast. It can be deadly.
I think it benefits a lot of conditions, but if you have a condition, it's also potentially dangerous to try it and we need to get a lot more savvy about how people with conditions can safely try it.
With asking around about Refeeding Syndrome and some best practices for how to effectively break a fast plus some experience, breaking a fast has gotten to be a lot easier on me.
I could have potentially died from fasting and it likely wouldn't have been blamed on fasting. My condition is serious enough they would have blamed my condition.
But it has proven beneficial and I hate it less than I used to.
The logic behind this is that the turmeric and ginger causes a (very mild) inflammatory response in the stomach. It gets the body "ready" for food again.
The bone broth supplies a very mild, easily digestible form of protein that resupplies immediate deficits. Sauerkraut supplies good digestive bacteria to rebuild your population of digestive helpers. This helps prevent diarrhea, though not entirely.
Almonds, pumpkin seeds, sunflower seeds (preferably unsalted) begin supplying dense packets of minerals. Don't have too much, but a few handfuls will be a good start.
Avacado! Calories (from good fat) and minerals, and more fiber.
The soup is the first serious nourishment. The tofu, chard, kale, and napa provide a range of good stuff. Protein from the tofu, and more minerals and fiber from the leafy greens. Lightly salted broth, (a mix of bone broth and chicken broth for flavor) is also good.
Yogurt (active culture) provides calcium and fat, and another excellent boost to helper bacteria.
More snacking on the nuts and seeds as you like...
A light dinner of thin slices of ribeye with onions and soy sauce over rice, and a nice cruciferous vegetable blanched, dressed with a touch sesame oil and salt.
Rebooted!
The waits in between are important, as is continued hydration along the way.
All that said, many of the benefits you supposedly get from 3-day / 5-day fasts, can be had from reduced calorie diets.
> I still have extremely severe diarrhea when I resume eating.
Try resuming with an at least slightly green banana. It's a really effective tool vs. diarrhea in general, but I've found it to also be a great restart after fasting.
Definitely not. Nutrition and dietary studies are famously hard to draw any solid conclusions from due to the logistical challenges of performing quality studies (randomization, blinding, "placebo" effects, adherence, follow-up, ...). Additionally, do we assume these effects are consistent for everyone, or certain age groups, genetic markers, ethnicities, etc. Even within individuals, would effects be beneficial for the whole lifetime?
It seems balance and "do what works for you" would be the recommendation.
A mouse starves to death in 48 hours. I have gone 12 days without food (water fast) and was not even close to starvation. Probably could have gone another few weeks before I expired.
I would say 16 hours for a mouse is probably more like 7 plus days without food for a Human.
I started experimenting with fasting a about 2-3 years ago. My initial goal was weight loss (lost 100lbs from 272->172). My limit was typically 7 days but I wanted to see what the impact of a longer fast would do in the area of autophagy. I experienced some positive results but would discourage others from doing it, 3-5 days is more than enough. I would also discourage doing alternate day fasting or 24 hour fasting since it will screw up your metabolism (I ate 2 meals (2500kcal) every other day for 3 months) and found it very stressful on my general well being and metabolism.
These days I maintain 172 lbs with time delayed eating (18/6) and a clean diet.
Main goal for these kinds of fasts is weight loss, reducing insulin resistance and particularly extended fasts to achieve autophagy where your cells do internal house keeping to clean out broken cellular components and repair themselves.
My 5 -7 day water fasts helped with some minor skin issues and I have no joint pain anymore, but that might be from losing some serious weight. For every 1 pound of body weight you lose, I have heard it removes 4 lbs of pressure on the knee and lower back. My 12 plus day water fast cleared up any remaining skin blemishes and a little Vitiligo between my fingers disappeared. I'm thinking after a year of monthly 5-7 day water fasts (18/6 Time delayed eating the rest of the time), the 12 day water fast was incredibly impactful, it felt like my body was pushed to use anything it could at that point to fuel itself.
My only regret is that I wasn't able to have someone doing a study or researching fasting monitor and harvest the wealth of information that was available.
I seems like the skin pigment returned to almost normal. It is just a shade lighter than the surrounding skin but otherwise unnoticeable. I of course can see the ever so slight difference since I know where to look and it was basically bleach white before, especially as the surrounding area got sun tanned.
I have heard one of the causes of Vitiligo might be the liver and if this is the case then maybe fasting restored my liver health which promoted the healing? Just my guess....
I fast pretty easily from 6pm to noon the next day. So I would be getting an awesome 18 hour fast daily however I have coffee with milk at 8am. Am I cancelling out those last 4 hours?
I hate black coffee so I’m not sure what I could do.
Maybe. I think in the study the rats were fully fasted, so you’re into unknown territory as far as the study goes. But I also assume you’re not a rat, so that’s not exactly the biggest difference.
There are lots of definitions of fasting and it’s not perfectly understood which consequences line up with which behaviors.
It’s pretty clear things are different once you break down the different ideas of “fast” and build it back up. In a dry fast, nothing enters your body except air. Now switch to a water fast and your stomach and kidneys are going to start doing something with that water. Have some coffee and now your liver is processing that caffeine and other chemicals. Add some calories (milk) and more organs are doing more. And then once you get past 500 calories in a day, you’re not really fasting by just about any definition.
So your coffee is doing something, the milk is doing something, but I don’t think it’s perfectly clear what happens at each threshold.
> It’s hard with a family though if they’re on different schedules.
My approach was that the kids ate things I wouldn’t and so it wasn’t difficult for me to be present and not eat.
And pedagogically it was apparently better than eating, say, just salad or a minuscule serving of the meal, as their mother was concerned about modeling behavior that might encourage diet pathologies (e.g. anorexia).
No real dinner, just a snack in the afternoon. But yes, breakfast and lunch are a bit heavier. When I think about it, maybe it works better now because of lockdown and WFH...dunno
Take pills of pure caffeine. Easy and cheap to find on any drugstore or Amazon or any specialized online shop.
I stopped taking roasted coffee because i got concerned about acrylamide and now doing much better on just pills of caffeine.
lol, exactly same diet with the same coffee problem here. I'm constantly told that "coffee is fine" whenever I ask. But milk is still food and not a "drink" so switching to black would be the only acceptable solution. sigh.
Per the figures, it looks like 16 hours had the largest effect, even larger than 24 hour fasts. But this is mouse data and should all be taken with a huge grain of salt.
Off topic: I understand “taken with a grain of salt” is meant to express diminishment of the idea it is being associated with. By saying “huge grain of salt” which is very common, doesn’t that defeat the purpose?
They considered 12hr a fast. So finishing dinner at around 7 and eating at 7am next day is considered a fast? Easier than I thought about what a fast would be like
In previous rodent studies, intermittent fasting (IF) was found to stimulate production of neural stem cells in the hippocampus, which is a portion of the brain critical to memory formation. This study measured apparent IF-induced changes in a particular type of molecular communication (the Notch signaling pathway) that the body uses to tell itself to increase such stem cell production.
Very important to note that the non-fasting mice were significantly less heavy:
>Compared to AL [ad libitum, "at one's pleasure"] mice, IF12 [12 hour fast], IF16 [16 hour fast], and EOD [24 hour fast] tamice demonstrated significantly lower average body weight after 3 months of IF (Data not shown).
So this could be due to lower overall caloric intake.
Fasting prompts significant release of growth hormone, so it is not surprising that it promotes cell regeneration, but interesting to see it applied to synapses.
The title for a news site and the title for a scientific journal needn't be the same. The title here should absolutely reflect the fact that the study was in mice.
It makes sense that food deprivation stimulates hippocampal neurogenesis, because in the absence of food, a mammal has to go to new locations to find new food sources. That requires navigation and memory mapping, both of which are core functions of the hippocampus.
Im not sure, if what the research here observed is real, stand-alone "neuro" genesis.
Several animal species, in times of hardship (like migration) reform their brains, by forgetting unimportant memories or reduce brain area dedicated to now unimportant skills. Quite similar to a stroke victim, that relearns speech, by "re-purposing" a different brain area.
Fasting indicates a food scarce environment, so the brain might do the same thing every body does - and reduce calorie consumption in all areas, including the brain. So the "reconnection" might just be a side-effect of the "down-sizing".
> Adult hippocampal neurogenesis is a process that describes the generation of new functional DGCs from adult neural stem cells through the amplification of intermediate progenitors and neuroblasts, as well as the integration of these new neurons into the existing neural circuits.
Source: https://www.nature.com/articles/s41380-018-0036-2#:~:text=Ad....