Wednesday, June 4, 2008


Why are we so soft today? Why is it that our ancestors were able to perform feats like killing bears and wooly mammoths in snow-swept grasslands? How do present-day tribesmen withstand days of ultra-cold temperatures in Northern Greenland and prolonged periods without water in scorching hot Kenyan deserts? Why is it that a century ago, children in the Swiss alps ran barefoot through ice-cold mountain streams on cold days, while now they get carpal tunnel syndrome playing video games? How did they do all this without succumbing to the chronic diseases that are so rampant today? I believe part of the answer lies in hormesis.

Hormesis is the process by which a mild or acute stressor increases resistance to other, more intense or chronic stressors. It can increase resistance to a variety of stresses, not only the one to which you are exposed.

It might sound like a foreign concept, but you're more familiar with it than you think. Exercise is a form of hormesis. It's a stress placed upon the body that increases resistance to a number of other stressors: physical exertion, cardiovascular disease, depression, diabetes, age-related cognitive decline, neurodegenerative disease, etc.

Intermittent fasting is one of the most promising forms of hormesis. It's consistent with the variable energy intake our hunter-gatherer ancestors probably experienced. As with some other forms of hormesis, it has broad-ranging effects on health and stress resistance. Alternate-day fasting, a version in which food is available for 24 hours
ad libitum and then not available for the next 24 hours, increases mean lifespan in mice under some conditions without reducing calorie intake. It increases resistance to neurodegeneration, stroke, myocardial infarction, toxins, cancer and diabetes in rodents. It increases the expression of heat shock proteins and SIRT1, both implicated in general stress resistance. Basically, it makes them tougher all-around.

Although only a few studies have been performed in humans, IF
looks promising for preventing or reversing diabetes, cardiovascular disease, overweight and possibly other health problems. It can also decrease fasting insulin and increase insulin sensitivity considerably. I fast for 24 hours, once a week. No calories, only water. It's not a form of caloric restriction, because I eat like horse the day after fasting. It's just a mild stressor that toughens my body to other stressors.

I also take cold showers. Here the scientific data are more sparse, but it has a long history of use as a form of "body hardening". I do it to increase my cold resistance by firing up my
non-shivering thermogenesis. It seems to be working. It certainly wakes me up in the morning! Have you ever noticed how you can get into cold water and be surprisingly comfortable once you're used to it, even though you're practically naked and water is conducting heat away from your body 20 times faster than air would? That's probably your non-shivering thermogenesis kicking in.

There are probably many other ways to induce hormesis. Do any of you have techniques to share? By the way, hormesis is one of the central tenets of homeopathy. Solid principle, incorrect application. I'd be happy to sell anyone sugar pills for 50% less than his or her local homeopath is selling them. I promise mine are equally effective...

Soft living makes a soft body. Give it some controlled stress from time to time!

Thanks to Kirill Tropin for the CC photo.


Unknown said...

The "hygiene hypothesis" describes how the full activation of the immune system is a form of hormesis. When we're shielded from disease from an early age by antiseptic environments, immunizations and antibiotics we later become more susceptible to conditions such as allergies, asthma, atopic dermatitis and possibly many others.


Nick said...

Do you have to worry about muscle loss while fasting? Does it depend on the length of the fast?

Adam Steer said...


Thanks for a great post. This is one of the main reasons that I have become so attracted to fasting. I've added this post to my Squidoo Lens on IF. I won't post a link though unless you give me the nod. Although it is centered around the Eat Stop Eat method, there are open link "plexos" to any and all information related to IF.


Debs said...

I didn't know there was a word for this! I love it.

Challenging your brain seems like a pretty clear form of hormesis. Be sharp in one area, it will help you be sharp in others (hooray for synapses). Swimming in cold water too. Living outside your routine, for that matter.

(For the record, I have speared and killed every single woolly mammoth I've ever met.)

Stephan Guyenet said...


You're right, the idea fits in really well with the hygeine hypothesis.

Stephan Guyenet said...


I wouldn't worry about it. You should be burning mostly fat. Anecdotally, some of the most muscular semi-hunter-gatherers (in Papua New Guinea for example) won't eat for 24-48 hrs if it's raining and they don't feel like going outside their huts. Read Art DeVany's blog if you want more info on lean muscle mass and IF.

IF also increases growth hormone. It may not be the best path if you're a bodybuilder, but you can be lean and muscular on an IF regimen.

Stephan Guyenet said...

Hi Adam,

I don't know what a Squidoo lens is but you're welcome to link to the post from wherever.

Stephan Guyenet said...


Probably so. Use it or lose it.

Unknown said...

Regarding stressors involved in hormesis, I think it's important to make a distinction between "natural" and "unnatural"; natural as in stressors we're evolutionarily adapted to. Unnatural ones such as prolongued sitting, pollution, processed foods, electro-smog, sleep deprivation etc. seem to have an effect that's the opposite of hormesis.

Stephan Guyenet said...

Thanks Reid, that's a good point.

Anonymous said...

I am quite fortunate to live 5 minutes walk to the gym where I work out, and it has a sauna (180deg), steam room (110), hot tub (102), and a cold pool (40 deg). After my intense 30-40 min resistance workout, I go to the sauna until I begin to feel very uncomfortable and stressed --usually 8-10 minutes. Then, it's 3 minutes in the sauna, much higher humidity though lower temp so the stress increases. Then the hot tub, where even lower temp still, the efficiency of transfer is far greater, so the stress continues.

Then, it's right into the cold dip in one single shot. Never wade in. Submerge the head. I liken it to a grueling chase for prey, and once given up or caught, diving into a spring run off stream if one's available.

Anyway, I easily stay in for three minutes, and actually, only the five 5-10 seconds are a shock, and the rest of the time feels wonderful. It's a complete reset button. I go in feeling light, hot, stressed, somewhat weak and come out 3 minutes later feeling like I could easily go do another workout. No sweating either. The "cool down" period is done. In the winter I often go less time. Even 30 seconds is enough to reset.

To the guy who wondered about fasting making you lose muscle, no way, not if done right. I'm still at about 20% BF, so a way to go (began at over 30% BF), but I never gained so much lean and so much strength until I began fasting last January, which I do twice per week, 30-36 hours, and always end it with my twice weekly high intensity workouts. Working out hard without having eaten a thing in 30-32 hours is something everyone ought to try. Do it four times, you'll never want to work out on anything but an empty stomach again. Ten minutes in and any hunger is gone, until 2 hours or so after the workout. I never eat after until at least a couple of hours have gone by, and sometimes I wait up to six.

Stephan is right: we're so pampered. We've grown soft and have been fooled into thinking that everything we evolved to handle very well is going to harm us.

Stephan Guyenet said...


Thanks for your perspective. That's a pretty intense routine! I wish I had a cold pool to dive into; right now I have to settle for my wimpy low-flow showerhead.

Billy Oblivion said...

I've been doing a 20-24 hour fast once a week for the last 4-5 weeks, and I do think it's helping somewhat.

Cold showers OTOH just suck.

I've spent enough time in places where a nice hot shower was an incredible luxury, and even a luke-warm dribble was more than you could get most of the time that I'm not going to deliberately pain myself.

I'll swim in cold water, I'll occasionally finish a shower at the gym with a cold rinse (especially after being in the sauna), and I'll ride my bicycle in what passes for a cold rain around here (San Jose/San Francisco area), but my morning shower? Nah.

Nick said...

Stephan, this post has me curious: Suppose I fasted for about 24 hours, and then had a big dinner that evening (a low carb dinner, that is). After feeling refreshed, suppose I decided to fast for another 24 hours and load up on food at dinner tomorrow. And I repeat this over and over. That is, how would one fare on one meal per day, assuming a low carbohydrate intake so as to prevent insulin spikes after those big meals?
And in general, this begs the question of how many (or how few) meals is healthy? Does one really need to eat 5 or 6 meals a day if they are low carb meals?

Stephan Guyenet said...

Hi Nick,

It probably doesn't matter much whether you eat three meals a day or one as long as it's healthy food. I think more than three is pushing it though.

The idea behind hormesis is an acute, intermittent stressor. If you're eating one meal a day every day, that's a chronic behavior rather than an acute one. I think you'd be better off mixing it up.

Debs said...

As I write this in the wee hours, I think one natural stressor that's not healthy is reduced sleep. I'm not saying there aren't good reasons to lose sleep now and then (or bad ones), it just doesn't seem intuitively positive the way cold water or fasting does.

Reid, I like the distinction you made.

sam said...

IF sounds all well and good, but I have a super fast metabolism and have always had to eat a LOT to gain even a small bit of weight.

If I started introducing a day of fasting each week my strength gains would go out of the window.

If I go to the gym to do let's say 5x5 deadlifts, and I haven't eaten well that day, then I can goodbye to any PR's.

IF may be good for some people, but for any "hard gainers" or people with above average metabolic rate, it's just a disaster.

Stephan Guyenet said...

Hi Sam,

If putting on weight is your goal then I agree, IF is probably not for you.

Anonymous said...

I was linked to your blog from this weekend's link love at Mark's Daily Apple. I had never heard of hormesis although I was aware of the specific benefits of some forms of hormesis like exercise, intermittent fasting, and cold showers.

I will continue browsing around your blog and return to keep up with new postings.

Jeff said...

I do the IF and cold water therapy. Another one I am adding to harden myself is going barefoot as much as possible. After a workout in my gym at work I walk outside for 10-15mins without shoes. Ground is rough and I purposely walk over the rough spots.


JLL said...

Your idea of cold showers doesn't seem so appealing (though I'm not saying it doesn't work), but I've been doing intermittent fasting for some months now.

Instead of fasting for 24 hours just once a week, I fast for 24 hours, eat for 24 hours and then repeat.

So if I start eating at 4 PM on Monday, I will stop eating at 4 PM on Tuesday, and start eating at the same time on Wednesday again. Works great.

Hunger doesn't seem to be an issue for me anymore. You get used to IF after a few months, but I've found that coffee is the most efficient way of reducing hunger. It really works. Black tea and green tea work too, to a degree, but as I suspect the appetite-reducing effect is due to caffeine, it makes sense that coffee works best.

patrea said...

Also, Tabata and GPX are highly effective exercise rountines. The point is that you strain to the absolute limit of endurance. A cold bath works well too.

Ken said...

Michael Ristow has done some interesting work with a zero carb diet (for worms admittedly), where the oxidative stress from being denied carbs turbo charged their metabolism. The effect was nullified by supplying antioxidants. He also did a recent study where antioxidants prevented exercise from improving the insulin resistance of humans.

"I fast for 24 hours, once a week. No calories, only water. It's not a form of caloric restriction, because I eat like horse the day after fasting. It's just a mild stressor that toughens my body to other stressors."

Periods of food shortage tend to be prolonged and seasonal for hunters. Starting as food became gradually less ketones would rapidly rise during a period of food shortage - maybe this is protecting the brain cells.

Repeated 24 hour abrupt total fasts started with full glycogen stores (suppressing ketones) - hmmm.

Stephan Guyenet said...


Some hunter-gatherer groups fasted regularly. In the Pacific Northwest, it was common for hunters to skip a day of food, often because they felt it improved their hunting.

Venkat said...


Another informative post.

Can you provide details of your IF? When do you stop eating? If you decide to fast on Saturday - when do you start fasting and when do you start eating? Because, do you stop eating Friday 8 PM and start again on Sunday 7 AM or Saturday 8 PM?

Other than the hormesis, do we have any other advantage of IF?



Unknown said...


Great post. I'm not sure I agree that homeopathy is based on the same principle as hormesis. Hormesis is based on scientifically measureable dose response curves showing a beneficial effects at low doses that are biologically meaningful. However the dilution factors used in homeopathy are so large that not even one molecule of the substance is present, so I think it is pseudo science

By the way there is an interesting blog on the application of hormesis on a site called "Getting Stronger". The author has developed this into a whole philosophy called Hormetism.

cassan said...

I've often heard that mountain-dwelling people tend to live longer than folks at lower elevations. Not sure if this is validated by the literature, but it makes sense, no?

Living at or regularly ascending to high altitudes is probably a form of hormesis as well. Does anything you've read attest to this Stephen?


Unknown said...

I grew up in Houston, which gets fairly hot, back when central AC was just becoming affordable. Since our mother was from the north, she wanted central AC so badly that she picked up extra shifts at her part-time job. I remember many visiting, walking around the house to see what it was like for the house to be cool through-out.

I do remember school activities being limited during heat waves. I don't remember the exact details, but something like 91-95F we'd take it easy but still do our outside activities, only staying inside when temps were over 95-96F. I hardly remember any kids passing out from heat exhaustion, our teachers/coaches did watch for it and had us take plenty of water breaks of course. Most schools didn't have central AC yet, but were putting it into the new schools when I was in high school (not mine, they have it now though).

Skip to today, where all but the poor has central AC. I believe most schools have central AC too. I've been noticing over the last 10 or so years that every spring or early fall, there's many reports about kids passing out from heat exhaustion.

I think it's possible that the kids aren't being exposed to heat like their parents and grandparents were, lowering their heat tolerance.

Te4t0n said...

There is BBC program on tonight about IF:

ecksocal said...

Could food be considered a stressor also? I wonder if our constant consumption of food due to the convenience of modern society is hurting us? When we eat it alters our blood glucose, more or less, which means it disrupts homeostasis? If you stress the body too much, it loses its ability to recover and compensate. If you apply this idea to glucose/insulin or our energy system in general, could you say the constant intake of food constantly disrupts the bodies energy homeostasis? Essentially, the pancreas would lose the ability to respond to the incoming glucose from constant stress from constant food intake by not secreting enough insulin, and thus blood glucose rises out of control, and all the other problems associated with it.

John Dorfner said...


While hormesis is NOT "one of the central tenets of homeopathy", there has been some significant recent research which tries to understand the connections between hormesis and homeopathy.

I direct you to

The central tenets of homeopathy are "like cures like" and the "minimal, single substance dose".

Just to clarify from my own understanding of the subject:

A hormetic dose is an amount of a substance which lies below the toxic threshold, and is given to a healthy person in order to produce, over time, the effect opposite that of the toxic dose, so that, if that person were to become exposed to the toxin, or stressor, he/she would have some built-in immunity or beneficial conditioned response.

The homeopathically prepared remedy is definitely administered in a quantity below the toxic threshold, but is given to a person who is showing the signs and symptoms of what it means to be "poisoned" by the original substance. The action is less about conditioning of the organism to the hormetic stressor than it is about the organism's response to the remedy, a secondary effect in opposition to the remedy, which causes the disease picture to be eliminated. It does not presuppose that the person had been, or will ever be, exposed to a toxic dose of the original substance.

Also, read:

Luc Montagnier won the Nobel Prize in 2008 for discovering the AIDS virus. He writes, "I can't say that homeopathy is right in everything. What I can say now is that the high dilutions (used in homeopathy) are right. High dilutions of something are not nothing. They are water structures which mimic the original molecules."


Tim said...

Just look what you've done: after reading this fascinating post I instantly felt the desire to have a cigarette with my green tea. Damn! ;)

Anonymous said...

Other ideas for healthy stressing:

1) Hanging upside-down
2) "holding it" for awhile instead of going to the toilet right away
3) Sleep on the floor
4) Going without eye glasses for a day
5) Holding your breath
6) Eating stuff that was dropped on the floor
7) Trying to see in the dark without a flashlight
8) Trying to see in full sunlight without sunglasses
9) Opening eyes underwater while swimming

I am not a doctor and do not recommend anybody do any of these things.

Bruce said...

1.Donating blood.

2.Training at high altitudes.

3.Reading at night with no lights.

4.Sitting in the snow.

5.Shooting practice. Trying to read something at great distance. (kids losing eyesight today, because of staring at a screen all day)

6.Isometric exercise.

7.HIIT and supercompensation.