The Iceman

Wim Hof can raise or lower his body temperature at will, overriding his autonomic nervous system. He is able to sit in a box of ice for almost two hours. He can swim 50 meters under arctic ice. Wearing only shorts and going barefoot, he has run a marathon in Lapland and climbed through snow to the summits of Mt. Everest and Mt. Kilamanjaro. In carrying out these feats, he is able to avoid hypothermia, the normal human response to extreme cold. Monitoring by physiologists show that he keeps his core temperature constant and normal during these challenges.

Yet Wim is not a genetic freak or Tibetan monk. He is a 52 year old Dutch man without much body fat. He believes that anyone can adapt to the cold and learn to control body temperature.

In this article, I will try to answer two questions:

  • How does he do it, and can anyone really do the same?
  • Is this basically an impressive stunt, or is there any benefit to learning Wim’s methods?
I will end by reporting on a preliminary experiment of my own with cold exposure.


No stunts.  First, just to be clear about what Wim has been able to accomplish,  take a look at these two short videos:

1. Wim running a half marathon in the north of Finland:

2. Wim swimming 50 meters under arctic ice:

An enjoyable account of Wim’s remarkable adventures and methods is detailed in the book Becoming the Iceman, co-authored by Wim Hof and Justin Rosales.  Rosales is a college student who became so intrigued with Wim’s abilities that he managed to earn enough money washing dishes–while still attending classes–to travel to Europe and learn Wim’s methods.  The chapters alternate between those written by Wim and those by Justin. While their account suffers from a lack of editing and is sprinkled with grammatical errors, the excitement of Wim’s remarkable sense of fearless adventure and Justin’s learning process make this book a real page-turner.

Changing how body temperature is regulated.  How does Wim Hof manage to keep his core body temperature elevated, maintain peripheral circulation, and avoid frostbite and hypothermia?  Nobody knows for sure, but there is no doubt that he does it.  Dr. Kenneth Kamler, an expert on hypothermia, frostbite and high-altitude medicine, who has himself climbed up Everest, has observed that Wim’s trained body responds differently than yours or mine.

The normal response to extreme cold exposure starts in the peripheral blood vessels in the extremities  — the ears, nose, fingers and toes.  Blood flow in the extremities at first increases, in order to stimulate warming.  If the cold exposure is prolonged more than a few minutes, goosebumps and shivering kick in to induce warming of muscles and skin.  But if the exposure continues beyond that, a process of biological “triage” takes place.  To preserve the high priority  organs – brain, heart, digestive tract — the body shuts down blood flow to the extremities to prevent further heat loss. The peripheral veins snap shut to segregate warm interior blood from cold peripheral blood. After all, these extremities have a lot exposed surface area, so cutting them off greatly conserves heat.  But the cost of doing this is frostbite and the irreversible tissue damage that often results if the cold exposure is sustained for more than a brief time.  Finally, when the core temperature falls below 95 F, the various stages of hypothermia set in, ultimately leading to death if sufficiently prolonged.

But Wim, and Tibetan practioners of the ancient art of Tummo, are able to significantly alter this normal process.  As Kamler explains, the key adaptation occurs within the brain during meditation–specifically the yoga and controlled breathing exercises that Wim and the tumo practitioners follow.  Of these exercises, breath retention exercises are key.  As a result, there is a significant activation of blood flow and electrical activity in his frontal cortex and hypothalamus — areas that regulate peripheral nerves and veins involved in the regulation of body temperature.   Normally, the circuit between the hypothalamus and these temperature control circuits is involuntary, governed by the autonomic nervous system. Kamler reasonably speculates that,  through meditation, Wim is able to override the normal function of the hypothalamus, allowing the peripheral veins to remain open and heat the extremities, preventing injury.  He points out that Wim must be generating heat and distributing it more efficiently, but he admits having no idea mechanistically how Wim’s meditative techniques accomplish this.

The monks who practice Tummo are able to tolerate cold, but they do so in a meditative pose, while sitting. They speak of being able to generate an “inner fire”.  Wim Hof’s method has diverged from that of classical Tummo. He has innovated significantly, since he is able to control his body temperature while moving about, in fact while exerting himself under conditions of running, swimming, or high altitude climbing which would be challenging for most people even at ambient temperatures! Yet, while Wim is certainly a one-of-a-kind personality, he is insistent that anyone can apply his techniques. His success in teaching Justin Rosales and others seems to bear that out. More recently, Wim  has devoted himself to training others through seminars and training expeditions.

Other abilities.  Wim’s ability to voluntarily control what what we consider to be automatic, involuntary responses does not stop at tolerance of extreme cold.  He has also learned to tolerate extreme heat, consciously overcome pain and cramping, and even moderate his immune response to endotoxin.  A fuller discussion of these abilities is given in Becoming the Iceman.

Possible benefits.  I’m particularly interested in Wim Hof, because of my own positive experience taking daily cold showers.  As I discussed in my post, Cold Showers, making a daily habit of cold showering results in a remarkable degree of adaptation.  The initial intense discomfort of cold shock rapidly shrinks in both intensity and duration, and the self-heating process of thermogenesis becomes more prominent after only a few weeks of the daily habit.  I’ve found benefits in weight control, mood enhancement, and generalized stress resistance.  I’ve not had any colds since starting cold showers. When my family was suffering with a stomach flu that lasted several days, the net effect on me was a 12 hours of achiness which I slept off on a single night, with none of the nausea that they had.

Could more aggressive exposure to the cold provide benefits that go beyond that of daily cold showers?  Hof and Kamler have suggested that the ability to open up peripheral veins and capillaries may help to enhance more than just temperature regulation.  It likely improves blood circulation overall, particularly in the smaller peripheral vessels. Because there are so few individuals that do what Wim Hof does, there is not yet any body of clinical science regarding the benefits to circulation.  But it is not hard to speculate that cold exposure could be a great way to fend of a wide range of cardiovascular and circulatory maladies.  So it intrigues me.

Total cold water submersion.   Cold showers are great, but what Wim Hof does is far more extreme.  Not only is the temperature of the water significantly colder — 32 F vs. the 55-60 F of my showers — but the total body immersion involves much more extensive skin surface area contact, meaning more rapid heat loss. A few times a year, I go for a brisk 10 minute swim in the ocean.  Here where I live in northern California, the ocean temperatures range between 53 and 60 F, similar to my shower water, and ocean swims are definitely more bracing than the cold showers.

My first experiments.  I want to see if I can up the game beyond cold showers. I first read Tim Ferriss’s account of cold water exposure in his book, The 4-Hour Body.  In his chapter “Ice Age”, he recounts the method of Ray Cronis, a NASA scientist who was able to lose almost 30 pounds of fat — fat, not weight — in 6 weeks, by taking cold walks, cold swims, and by drinking cold water.  Ferris himself tried immersing himself in cold baths — with added ice — for 20 minutes.  But he first heated himself to the point of sweating by consuming a thermogenic cocktail of ephedrine, caffeine and aspirin.  So what Conise and Ferris did doesn’t really approach the level of unmediated cold exposure undertaken by Wim Hof.

I want to see how much I can directly adapt to the cold.  My first effort will be to attempt this without any special meditative technique or breathing method, and certainly without taking any thermogenic medications or supplements, as Ferriss did.  So I did my first experiment today, and here is what I did and what I experienced:

I filled a bath with cold water, which I measured at 58 F (14 C).  I first submerged my legs.  It was painful, so I decided to allow myself to adjust before filling the tub with more water. Fortunately, after about 2.5 minutes, my legs no longer hurt and by 4 minutes they felt a kind of paradoxical warmth and I could wiggle my toes again. So I filled the cold water up to my chest when laying back. I was completely submerged at 9 minutes.  At first, this was very uncomfortable, and I started shivering. I felt some numbness, but that went away and I was comfortable again at  14 minutes. I could easily flex my toes and fingers. I continued laying in the tub, submerged up to my neck. The sensation alternated between shivering and coolness. I stayed in until 20 minutes had passed from the initial plunge.

After I got out of the bath, I felt warmer and tingly at first. But 5 minutes after getting out and drying off, I started feeling very cold and shivering uncontrollably. I was not really expecting that; I thought I would instantly feel warmer, just as I always do after stepping out of a cold shower. But in the book Becoming the Iceman, Justin Rosales and Wim Hof describe a phenomenon they refer to as “the afterdrop”, an experience of getting colder after you emerge from cold water. This is exactly what was happening to me. I needed to  put on warm clothes and move around to fight off the shakes. I was still cold and shivering 30 minutes after emerging from the cold bath, and my fingers were stiff, making it hard to type up my notes.

However, a full hour after finishing the bath I started to feel great. I became warmer throughout the evening, even though it has been a chilly evening. Psychologically, I have been quite alert all evening long. So there is some evidence of adaptation, even though the experience has been quite different than what I would have predicted from my familiar habit of cold showers.

I plan to continue experimenting with cold baths over the coming weeks, varying both the duration and the water temperature.  I’m interested to see how readily I adapt, and what other benefits or problems occur along with the adaptation.



  1. Fascinating. As someone who was born and raised in the tropics, and now lives in Canada, I am very interested in this. I have observed locals have better cold resistance than most immigrants from warm places–call it lifetime training.

  2. Shadowfoot

    I have an interesting experience regarding cold resistance. For the past several years I have generally worn shoes as seldom as possible, even in the winter. Because of this, I am presently able to tolerate freezing temperatures for up to half an hour and temperatures around 40 and higher pretty much indefinitely. I even went sledding barefoot once.

    This is definitely an adaptation, as my hands seem to have a poor response to the cold, something I have been trying to improve with slow success.

  3. chuck

    Thx for this great write up. I have been interested in cold exposure for a while. I had done cold baths and they are definitely uncomfortable for the first few minutes. I am going to try one tonight with some added snow from outside.

  4. Deepak

    I have tried cold baths too a couple of times after reading 4 Hour Body but without using anything to increase my body temperature. I had similar experience that you mention here. After about 5min of immersing my whole body into water (except face), I didn’t feel cold any more. I was shivering for the next 1.5hrs after I got out of the bath though.

  5. Bill Strahan

    Something I’ve played with for years. I noticed when I got angry my body would heat up and I would start dripping with sweat. Being curious, I started trying to extend the process, eventually finding I could do it voluntarily. That probably happened over the span of a year or two.

    I worked another year or two at directing the heat at hands and feet, and eventually got to where I could snow ski in temperatures down to about 10f without gloves as long as my hands were dry. Once they got wet, the wind chill in that temperature while skiing was more than I could overcome. The hard part was being able to do it without continuous focus. I did want to enjoy the skiing, not just focus on generating heat. And it does require some focus.

    There are times my wife has curled up next to me in bed and said “Do that hot thing” because she’s cold, meaning heat myself up. Makes me laugh, but within a few minutes she’s scooting away saying she’s too hot.

    I don’t play with it much any more, but I can still break a sweat in room temperatures within about 5 minutes.

    It’s amazing what our bodies are capable of.

    • Jeff

      Thanks for ur experience! I tried to replicate nd did feel some improvement. I guess it’s the way we breathe when angry that creates that change. I hope to be able to get to your level and without messing my BP.

  6. Eric

    Todd, thank you for the blog – as a lifetime stoic I was amazed at your approach of combining philosophy with diet and exercise. I want to start cold showers but have a question. If I understand correctly you only take cold showers – how do you wash your self? I mean do you use soap and shampoo under cold shower just as usual? I find it very hard to rinse shampoo and soap off in cold water, so the question is – can I take warm shower first to wash and then a cold one after? So some reason I feel it will not be as beneficial. Would it be better to take morning shower warm and another one in the evening cold? I would appreciate your opinion on this.

    • Todd

      Hi Eric,

      I like hearing from fellow Stoics. I find Stoicism to be a congenial philosophy, but for some reason there has not been much interest in the Stoic philosophy by people posting comments here or on the forum. And yet it is a philosophy with enormous practical value.

      As to staying clean while showering cold: It’s not that hard. The key is to choose soaps and shampoos that work well at low or moderate temperature. I personally use coconut oil based soaps and shampoos, which maintain a good degree of surfactancy and “slipperiness” even in cold water. My favorite brands are Kirk’s Original Coco Castile soap and Suave Natural Tropical Coconut shampoo and the related conditioner. You may need to spend an extra 30 seconds lathering and rinsing in cold water compared to warm water, but that’s no big deal. If you are still not satisfied, then take a warm or lukewarm shower once a week or if you happen to get particularly sweaty or dirty.

      I’m not in favor of frequent hot or warm showers or “contrast baths” involving quick alternation between warm and cold baths. I may take a dip in the hot tub or take a warm shower once every 1-2 weeks. But if you get under warm water on a daily basis, this seems to impair your ability to adapt to the cold. Frequent exposure to warm water appears to undo or partially offset the advances made in cold water adaptation.

      The above comments are not based on deep science — just my personal experience! So I would be happy to hear contrary opinions.

      • Eric

        Thank you, Todd, for clarifying that. I too don’t think mixing cold and hot showers is a good idea – it made me sick with cold more than once. Years ago I read about Seneca’s life time long “cold plunges” in the river in any season, amazing how you came to the same practice and the same philosophy. I can only finish with “Vale, valete” – which never translated so accurately!

  7. Rodney

    Hi Todd!

    I really enjoy your blog, and the writing on cold tolerance in particular. I have Raynaud’s, which though minor, still leaves my fingers and/or toes completely white without blood flow after SOME cold exposure. The triggers are unpredictable, as sometimes minimal cold sets it off, other times I do fine with fairly cold exposure.

    Do you see any possibility that I could learn to moderate or eliminate this condition through cold showers, or cold immersion? My main concern is that the cold shower will trigger the Raynauds, then I don’t know if I should continue, or stop to restore blood flow.

    Any thoughts? I would love to be more in control with any cold exposure.

    • Todd


      There is actually some clinical evidence that cold immersion can reduce Raynaud’s phenomenon, at least in some cases. Here are the conclusions of research reported by Dr. Frederick Wigley in his column in The New York Times:

      Patients with Raynaud’s phenomenon will acclimate to cold temperatures. In fact, Raynaud’s is worse during shifting temperatures, such as changing seasons (particularly the fall) than in the middle of the winter. In one study, we tried to trigger an attack with cold exposure by putting the hand in an ice box. We found that during the first visit, it triggered an attack about 70 percent of the time; during the second visit, it triggered an attack about 50 percent of the time; and during the third visit, we could trigger an attack only 30 percent of the time. We think this reduction of success of our cold challenge was due to acclimation to the exposure.More interesting, a group tried to reduce Raynaud’s by putting the hands in warm water while chilling the body; after several sessions, the cold exposure no longer caused Raynaud’s. The investigators suggested they had trained the fingers to be warm despite being in the cold.

      I would suggest a gradual approach, building upon the Wigley study. It may take multiple exposures over several weeks, but see how it goes and let us know!

      • Rodney

        Thanks for the ideas! I will have to experiment a bit, and might even try some cold showers or body immersion just to see how I respond. I wish I lived near a cold lake or ocean, but I suppose a bath tub will have to do for now.

        In the meantime, I look forward to reading about your experiences and progress.

    • Lerner

      Rodney, there was an army doc who did some experiments with arctic troops in Alaska. IIRC, he had them somehow warm up their hands with real heat while associating some Pavlovian effect, then they applied the conditioned trigger when outside in the cold… something like that. I’d read it years ago.

  8. Rodney

    Todd, I have one other question about cold showers and cold immersion. In the winter my water is 54 degrees F., but in the summer it is usually 68-70 degrees F. Since I have no other sources of cold water, would the 68 degree water offer any benefit, or would I lose everything I gained during the winter months? I have read that there is an upper limit on effective temperature, and it seems like it was much closer to my 54 degrees than to 70.

    Does your water temp vary seasonally?

    • Todd


      Your questions about water temperature are good ones. I’ve seen different recommendations and theories about this, but I’m not sure there are any conclusive studies regarding the relationship between water temperature and various benefits. So I can’t offer you any definitive answers. But intuitively, I would think you would get less of a benefit from the 70 degree water than from the colder water. It’s probably something that both of us should continue to research. Perhaps others can comment.

      What I have been doing is adding progressively larger amounts of bag ice to my tub to lower the water temperature. I’m just experimenting for now, but it could get expensive unless you have a good ice maker on your your refrigerator.

      Have you tried any immersion experiments with your hand to see if it reduces the Raynaud’s symptoms? I’ve been doing whole body immersion in my cold baths, and it is getting much easier. But I’m interested to know whether immersion just hands or feet gives a benefit.


      • Rodney

        Thanks again, Todd. I still haven’t decided how to proceed. Evidence is hard to find in any great detail so I suspect I will just have to decide what to try and get on with it.

        The perfect temperature, whether to keep my hands and feet warm while cooling the rest of my body, trying just hands and feet immersion, taking cold showers, or doing complete body cold immersion are all unanswered questions.

        I think I might just start out with cold showers for several weeks since my water temps are 54 degrees this time of year. Then I can expand my variables as needed. Once my summer water temps approach 68-70 degrees I might try adding ice to full body baths or maybe just immerse my hands and feet in an ice bath.

        The anecdotal evidence you provided above about someone seeing Raynaud’s improvement with cold showers also gives me reason to try this first. If you have any better suggestions I am open to ideas at this point. I tried my first cold shower today and didn’t find it to be too bad, though it did trigger my Raynaud’s in all four extremities to a minor degree. Hopefully this will lessen as I continue the daily exposure.

  9. Lerner

    Ha! I knew that someday I’d run across people who do & think some of the same things that I do 🙂

    Sometimes when hiking near a frozen lake with a thawed shore, I’ll stand in it barefooted. After a few moments of my feet feeling extremely cold, the intense pain starts in – like a thousand needles. I’d wondered what must be the experience of people who fall in – which is apparently more cold-shock than pain, from accounts of Polar Bear Club types.

    I’d always meant to do a Polar Bear swim myself, and prep by running around first to get my internal furnace on. But somehow I never actually got to one. I have laid down in the snow without a shirt, and taken a nap laying in the snow with my coat on and my scarf for a pillow.

    I’ve taken cold showers in summer and autumn. After repeated exposures when it’s not new anymore, your subconscious is screaming “DON’T DO IT!”, but you go ahead and stoically do it anyway. I don’t know the temp, but it’d be whatever it is for water that comes out of the pipe below frostline in NE USA – which I’d presume is constant year round.

    This was fun to read, Todd.

    But a P.S. I once did have my index finger go completely numb for 10-15 minutes on a walkday of 15F and very windy. So I’ve learned to always be consciously prudent, too.

  10. Poins

    I’d like to believe anyone could do this, but I’m not sure. Until this Autumn I prided myself on not feeling the cold, sometimes quoting Scott expeditioner Apsley Cherry-Garrard, who said “Cold is a state of mind”. I was happily sitting in the garden reading in the British November. I didn’t dig over the garden and plant my bulbs till December and spent several days outside, not noticing my cold feet and hands. Unfortunately, I then suffered a massive attack of chilblains; never having had them before, it took me some time to realise what they were–they formed on all my toes, several of my fingers, my ears, and, eventually, on my nose.

    It does seem, however, that the cause was too rapid heating up, not the cold itself. I then learned–not as quickly as I might have done– that I could reverse the pain of the chilblains by putting them in cold water. I learnt that, on Google Books, in a book by an 18th-century Scottish doctor: modern advisors (who may know less than him, the complaint now being rare) advise against this, but I think they are wrong. Raynaud’s is different from chilblains, though it attacks the same extremities, but the sufferer of Reynaud’s above might try the same in the search for an instant quelling of pain. In short, with chilblains the problem is not the cold, probably, but the heat. I found I could only stop them hurting at under 63F–I learned to keep room temperature at about 61 for a happy medium. Unfortunately, the tissue damage caused by chilblains is irreversible, so I understand.

    * * *

    On Todd’s prolonged cold rebound after the bath, it doesn’t surprise me. A few years ago I drowsed off in an unheated house and, after who knows how long, slowly became aware that I was shivering, and not superficially; so I endeavoured to warm myself up by the normal methods. To my surprise, it was difficult to do so, presumably because core temperature had been compromised. The experience shocked me, because it showed how easy it might be to succumb to hypothermia unawares; it takes a grip on you by dulling your senses, and then it’s the devil of a job to recover. The shivering woke me up, and perhaps that’s part of their purpose. I hope you are right that we can strengthen the body to resist vulnerability to cold, but please be careful.

    • Pagnol

      You might want to put this Scottish doctor’s advice on Wikipedia. Certainly, many people affected by the condition will look up the relevant article, and appreciate any advice on how to treat this.

  11. cb

    A search of your blog shows no mention of Dr. Jack Kruse, whose work has many points of intersection with yours–comments would be of interest.

    for example, on cold–

    • Todd


      I’m quite familiar with Jack Kruse and have a certain affinity for his perspective, particularly regarding the central role of the hypothalamus in regulating fat metabolism. His latest post suggests benefits from cold exposure that are similar to what I have advocated on my blog. Jack is a smart guy and has done a lot of research into the biochemistry underlying the inflammatory process.

      I did post a comment last year about his position regarding intermittent fasting (IF) on the Discussion Forum for this blog:,264.msg2382.html#msg2382

      While I agree with Jack on many points, there are at least two areas where my views diverge:

      1. While I believe that leptin resistance and leptin resistance are two distinct but overlapping causes of obesity, Jack believes that ALL obesity results from leptin resistance, and that everyone with insulin resistance is also leptin resistant. Read my article “Obesity starts in the brain” for evidence and references that supports my view.
      2. Jack believes that if you are leptin resistance you must eat a high protein breakfast as part of a “leptin reset”, and that IF is not advisable until you first become leptin sensitive. I cannot find any evidence or compelling argument to support his thinking in that regard, although I am open to being persuaded. My own experience is that IF is helpful for everyone in lowering basal insulin, improving insulin sensitivity and leptin sensitivity, and inducing beneficial processes such as autophagy.

  12. cb

    thanks… Dr. Kruse’s view seems to be based on the goal of resetting the hypothalamus by consuming a high protein meal in the early morning, where normal circadian rhythms dictate a high protein meal in the early evening (see _Hardwired for Fitness_ by Portman and Ivy)

  13. cb

    Roman baths, as in Russia, Scandinavia, and German countries today, favored alternation between hot and cold. Germans call this Wechselbad–going from lying in the snow to a hot sauna or outdoor hot bath followed by a cold swim in an outdoor pool. There must be some benefits from heat (seratonin?) and benefits specific to the alternation between hot and cold.

  14. My Leptin Rx is a reset for rewiring the hypothalamus when one is LR. I would not expect you to find much on it because as far as I know no one has figure out or tripped over what I found out about this from a neuro-plastic stand point. Today I post my cold thermogenesis protocol. 18 months in training and I have found some amazing things. I have spent lots of money and time looking for Optimal. This bio-hack may be the best money I have ever spent. I can spend now up to 18 hours packed in ice. What my goals are in doing this are not what most are doing. This is about the neurosurgical correlates of the biology which I am going to lay out in excruciating detail soon………All obesity does starts in the brain and ends there too. There is no example in biology I have found yet that does not including all the genetic causes like Prader -Willi. Obesity is an inflammatory brain disease pure and simple. The more we learn the more I believe that we are converging on some big variables that will effect multiple avenues of molecular biology. The leptin Reset is brain surgery without a knife. It induces changes in everyone who is LR except those without an intact vagus nerve. Todays post fills that gap now too. Cold thermogenesis actually does not require an intact vagus nerve. I have close to 500 patients who have failed IF’ing while LR. In fact the internet forums are littered with IF failures. I have sucessfully treated close to 40 failure from If guru’s online. I am a huge IF’ing fan but it does not work well in those who are LR as I explained here……

    • Todd


      I’m happy to see your post on this thread, as I admire your blog and think you are one of the more innovative thinkers and experimentalists — not to mention clinicians — in the paleosphere. I’m happy to see that we have reached very similar conclusions on a range of issues regarding metabolism–particularly the origins of obesity as an inflammatory condition of the hypothalamus, and the value of cold immersion as a stimulus to metabolic re-programming. I was particularly excited to see the posts on your blog over the last few days regarding your experiments and protocols related to cold exposure. As you can tell from my blog, I’ve found my daily use of cold showers over the past two years to be transformative, and have recently been exploring a more aggressive use of cold immersion. I will certainly be following your research and revelations in that area.

      I did read your post on “Intermittent fasting and leptin” and related posts on the Leptin RX protocol, and find it very interesting. I do have a few questions, however.

      1. You take the position that leptin resistance underlies all obesity. While it is true that many of the obese are resistant to both leptin and insulin, there is some evidence — which I summarize in my post “Obesity starts in the brain“– that leptin resistance and insulin resistance form two distinct, but overlapping subtypes of obesity, associated respectively with subcutaneous and visceral fat depots. Those with dominant subcutaneous obesity, such as Sumo wrestlers, can be leptin resistant, but insulin sensitive. And likewise, there are many with insulin resistance who remain leptin sensitive, including many “subcutaneously lean” men with excess visceral fat. The distinctness of these two different etiologies of obesity is documented in articles by Cnop et al. and Woods et al. . What do you advise for individuals who are IR but have normal leptin levels, such as those in Cnop’s study?

      2. I understand and agree with your analysis of AMPk and mTOR as complementary regulators of appetite and nutrient oxidation (via action on the orexigenic NPY/AgRP neurons and the anorexigenic POMC/CART neurons in arcuate nucleus of the hypothalamus) in response to stressors such as exercise and fasting. One of the prime reasons I’ve given for IF is that it brings about beneficial autophagy, reducing the levels of glycated proteins and other metabolic “junk” within the cells, and autophagy occurs only in the low insulin state prompted by anorexigenesis.

      I further agree with you that leptin plays a key role in the regulation of the above regulatory processes: LR individuals will have a much more pronounced appetite and reduced tendency to oxidize fatty acids and build muscle, because the reduced levels of leptin shift the balance to the orexigenic neurons in the hypothalamus.

      But it seems to me that IFing, approached gradually and not all at once, should help build both leptin sensitivity and insulin sensitivity. I advocate approaching fasting gradually, by first cutting out snacks, and then gradually increasing the intervals between meals or skipping occasional meals. And one of the easiest to skip, in my experience, is breakfast. Skipping breakfast is especially beneficial because it effectively extends the reduced-insulin fat-burning state you enter during sleep. So why not extend it? Cutting it off early in the day by refeeding would seems to be counterproductive. And eating a high protein breakfast, even if carbs are low, will tend to raise insulin (even while also raising glucagon), effectively shutting off the benefits of autophagy.

      In short, while we both agree that it takes weeks or months for leptin sensitivity to be restored, based upon “healing” the inflamed hypothalamus, it seems to me that a gradual approach using intermittent fasting, cutting out or delaying breakfast early on, should be more effective than eating a big, protein rich breakfast, which will not drop basal insulin levels as quickly. And for individuals who are primarily insulin resistant, but not leptin resistant, I would think that IF would be especially useful.

      Of course, you have cited your own clinical experience with hundreds of patients who “failed” with IF, so I cannot doubt that experience. But I lost weight most easily using IF, and I also reversed markers of insulin resistance, including lowering my basal insulin from 15 to 4 units, dropping CRP and triglycerides dramatically, and raising HDL. I’ve seen accounts of others who reversed their diabetes by using a similar protocol. For an especially dramatic account, see this article by that of Lee Shurie.

      So I wonder whether the many “failures” of obese, leptin-resistant people trying IF are a consequence of trying to proceed too quickly, rather than taking a more gradual approach. I also would like to understand why you think high protein early in the day is so important, and works better than gradually moving back the first meal of the day, while cutting out snacks.

      Jack, I love to learn and have my views challenged, so I hope you will respond and let me know where you think I may be wrong in my above analysis and conclusions.



  15. I am fully aware of both of those studies but I guess where you and I differ big time is in using or thinking leptin levels matter. Dr. Rosedale popularized this. Generally most people can use this. But in this specific case leptin levels can lead you down the wrong road. If you go and read my site I have two posts that address why I do not use leptin levels. You will be fooled many times by them. One can be fully leptin resistant while having Leptin levels below ten. The key is understanding that anyone who has IR has a real problem with cortisol and leptin. Leptin controls PEPCK which is the rate limiting enzyme for gluconeogenesis is the best marker for leptin resistance for those with diabetes and IR (hepatic leptin resistance). The manner in which I diagnose this clinical scenario uses HS CRP, ferritin levels, haptoglobin, Vitamin D levels, and reverse T3 levels. If you asked me if any test by itself is best……they are not sensitive or specific enough by themselves but collectively they are powerful. But here is the big clinical point I make to other clinicians and I will make to you. Absolute numbers never trump clinical symptoms. When a number is normal but you have IR you know that at the receptor level you have a resistance problem. Most clinicians who deal with hormones know this. It appears this is not well known by PCP’s and most patients. Anyone who has IR has leptin receptor issues. The proof for you would have been labs but the real test is hormonal testing that would have uncovered it. You would have seen the yoru diurnal cortisol levels were off and this means your CRH is elevated. If you go back to my Hormone 101 post (written for a patient not a clinician). When CRH is elevated it completely turns off the thyroid at the brain level (TRH and TSH) and turns all T4 and T3 to reverse T3. When T3 is insufficient (with Vitamin A) you cant convert LDL to to pregnenlone……..or any other hormone in the chain hence the reason I check the last hormone in the process……..this tells me something upstream is radically wrong. It is biologically impossible to be IR and not have leptin resistance at the receptor levels. I know this is not discussed enough but these are clinical pearls that physicians learn with experience. If you read many anti aging books on hormone replacement or on body building forums you will see this concept over and over again. Thierry Hertoghe is probably the world expert in bioidentical hormone replacement and this is clearly outlined in his book written for the lay public too. It is my belief that Dr. Rosedale’s book and his opinion on using leptin levels to diagnose LR is an epic failure in most cases. The real reason this happens was not really known when Ron wrote his book but we do know it now and he needs to re address it so many people do not continue to make the error going forward. The reason is SNP’s found in receptor binding sites for all the hormones. THe leptin receptor has over 25 SNP’s that we now know about that can cause these results. The way you can test for this today has become quite simple and cheap. Ten years ago to get this data would have cost 1 billion dollars. Today a 200 dollar test can be done at to find out what SNP’s are in your genome that may affect your interpretation of your results.
    Ironically, if you go back and read the synthetic leptin trials of Amgen (pre SNP data too)…….their research scientists found the same issues to be true that I laid out here. This is why a synthetic leptin had little change in some patients and huge changes in other who we might not have expected. The Vitamin D receptor is now up to 38 SNPs and we found 8 more in 2011 alone.
    The world an internet forums are filled with people who have A TSH of 1.0 who are still hypothyroid because their LDL is high while their HDL is low with a high rev T3 and elevated HS CRP and low D levels. They remain frustrated because they are unaware of why this happens because their doctors do not know about it as well. Clinical response is not a function of the lab number (CW advice says it is) but it is a reflection of what occurs at the receptor level (evolutionary biology perspective). Most clinicians would never treat them for hypothyroidism because of the TSH level but they are hypothyroid because they are LR due to the elevated CRH at the brain level. There are three levels one can be LR at and all can be to different degrees. The brain, liver, and muscle levels. All three have different clinical presentations and symptoms. If you think you can stratify them by labs you are dead wrong. Modern medicine makes this error all the time and you read it in these two papers. They are poor papers because in their discussions neither one account for it. This is where a history and physical comes in and some detective work. I have no doubt that you used IF’ing to your benefit. But that tells me your IR was on a continuum that was not far down the metabolic turnpike and I’d love for you to get yoru SNP’s tested. You may learn something very valuable about you that cant be generalized to the everyone else. I have seen your scenario but it is rare. When it appeared we found some underlying issue with advanced testing that made sense of the clinical picture. By far most diabetics in this country are diagnosed too late. The best way to fix them is not IFing……it is fixing the leptin issue and then moving them to an IF platform. In the last 7 years I have not seen one patient with IR who did not have profound LR. This is not an either or situation. This is a continuum that we operate on as a patient improves their metabolic profiles. The best way to reverse a high T3, CRH and LR patient is not using an IF platform. Once LR is dealt with IFing is a great move.

  16. Sue

    Why high protein in the morning Jack – you failed to answer that or are you saving it for your book?

  17. Sue

    Todd, re your shower post is it okay to take a cold shower after sweating up a storm exercising – I am sweaty and red-faced? Or should you have a cold shower when your body is at a normal temp?

    • Todd


      I think it’s fine to take cold showers either way. It’s a great cool down after exercise and certainly helps reduce post-exercise inflammation or muscle soreness. And it feels great. So by all means do that. But I think you get an even greater benefit by taking cold showers (or cold baths or swims) when you are not “pre-warmed”. Thermogenesis and cold adaptation are more readily activated, and you get the benefit of becoming progressively more tolerant of cold temperatures. As a morning routine or ritual, cold showers make you alert and energized every day. They’re a great antidote to depression or the blahs! For more benefits, read my post on Cold showers.

      • Sue


    • Andy

      Hi Sue, answer is here:

      Basically the RX uses the brain’s ability to rewire in an attempt to fall back to it’s childhood method of accounting for energy. Several factors come into it but most importantly vagus nerve stimulation at the correct (day/night light cycle based) time, control of night time light and low carb to avoid upping NPY and blowing your SCN’s perception of what time of year it is/how long the day is.

      “If one eats with a certain regularity (Leptin Rx) and makes sure it is tied to the sleep wake cycle, we can retrain the brain to account for food using older evolutionary pathways.”

  18. I just wanted to mention that I thoroughly enjoyed your most recent post concerning The Iceman. I was referred to your site via email by someone in your audience. It’s very encouraging to hear that others are just as interested in the cold as we are.

    I do hope that you continue to grow in your cold endeavors and that you learn, just as we did, that the cold doesn’t have to be an enemy, but a warm friend.

    • Todd

      Thanks for your comment, Justin. I really did enjoy your book, “Becoming the Iceman“. It is three books in one: a great resource on cold adaptation, a thriller-adventure story, and a diary of personal reflections. I hope that many people read it and enjoy it. The subtitle of your book — “Pushing Past Perceived Limits” — echoes the philosophy of Hormetism I espouse on this blog: learning to thrive on stress.

      I think that adaptation to the cold is one of the best examples of hormesis I’ve encountered. We are only beginning to understand the potential benefits of cold exposure, based on a very small number of true pioneers such as you and Wim. Your book taught me to push further than I already had with my daily cold showers. I’ve continued to make progress and will be posting a follow-up column shortly.

      I would be interested to hear more about what you and Wim plan to do next!



  19. Mark L.

    Since 2008, I have been ending most of my morning showers with cold water; the temperature of my water (which comes from a well) is about 51 degrees. For the last 18 days, your post has inspired me to be more regular, to do 2 cold showers per day, and push myself to be uncomfortably cold on my most sensitive areas (which are the area around my nose and the back of my neck). I hope my experiments lead to getting significant benefit without spending very much time and without having to dip myself into ice water. I have noticed a few things since going to 2 cold showers per day such as my facial skin feels tight for hours after a cold shower; a greater uptick in mood; and taking a cold shower before going to bed seems to decrease my need for sleep. I was hoping that the cold water on my chin would stimulate antioxidant production to change the gray hair in my goatee to brown, but alas it has not happened yet.

  20. Poins

    Well, since I commented here a couple of weeks ago, I’ve read the book and looked up a bit of research around acclimatization. Love the book–yes, it’s poorly written and edited, but the subject matter is gripping and the protagonists endearing. What’s exciting to me is the usefulness of the book’s ideas. I had already permanently damaged the capillaries in my fingers by cavalier mismanagement of cold, but I’m encouraged to see that Wim Hof hasn’t been much indisposed by the attack of frostbite he describes. I’ve no intention of becoming an iceman myself or starting to take cold showers, but I believe that by a modest application of the principles expounded in the book I coulkd maybe take several hundrerd pounds a year off my heating bill. I read the book in the open air in February, for example, and afterwards my house felt warm without the heating on. I’m convinced by the book, and by the science of cold adaptation, that I’d be doing myself no harm, and likely some good, by increasing my tolerance of cold.

    The only place Wim Hof lost me was when he claimed he can alter his immune system by acts of willpower and meditation. It seemed to me rather that his immune system fought off an injected toxin because of its cold adaptation, not because of Wim’s mind power in fending it off. For me that explanation makes more sense and is more remarkable than any mystic mumbo jumbo that Wim might have picked up from Tibetan monks.

  21. cb

    wim looks to be in good shape, but overtrained

  22. thernonaut

    Say what?

    From Wikipedia re Wim Hof:
    Hof holds eighteen world records including a world record for longest ice bath.[1] He broke his previous world record by staying for 1 hour, 13 minutes and 48 seconds immersed in ice at Guinness World Records 2008. The night before, he performed the feat on the Today Show.

    From Jack Kruse:
    #22 11 February 2012 18:47
    …I can spend now up to 18 hours packed in ice….

  23. bard

    Dr. Kurt Harris vs. Dr. Kruse

    see some more comments below this one…

    It is in fact entirely possible someone will kill themselves doing extended cold immersion in a tub of ice water. Mountain climbers, scuba divers, and sailors, hell, boy scouts and deer hunters are all taught about how deadly hypothermia is as part of their education. Every summer, someone dies a few hunted yards from shore right near my home in lake michigan. Water temp usually about in the upper 50s F. Not ice water. Summer kayakers with PFDs on.

    Some dummy (we see them posting here already) emulating Jack is going to fill a tub with ice water and lay down in it. Once the core temperature drops enough, the brain’s metabolism slows to the point that executive function – judgement – is clouded and the person may literally not have enough sense to get out of the tub, and they die. This actually happens in polar exploration and winter mountaineering. Without comrades around to put a blanket on you and start a fire, you die of NOT BEING ABLE TO THINK CLEARLY. This is how hypothermia kills. Hypothermia can also induce arrythmias.

    Then there is the less serious, but also not funny, issue of frostbite. It sounds all cutesy and harmless – frostbite – but it is a serious medical diagnosis. Even without tissue freezing solid, one can get vascular thrombosis and permanent tissue damage including damage to nerves and blood vessels. Permanent numbness, loss of sensation and poor blood flow can result. The idea of subjecting an extremity to this TRAUMA, even if your core temperature remains normal, is no smarter than striking yourself with a hammer or holding your hand over an open flame a la Gordon Liddy.

    So while the MRSA injection claim is not likely to emulated, these David Blaine cold stunts are.

    Don’t be stupid, people. You’ll feel really foolish with permanent numbness even if you don’t die.

    • Troy

      Very good points, Bard. Personally, I’ve been taking cold showers for a few months, and I absolutely love them.

      Started with hot first, then switch to cold… now straight to cold. Personally, I don’t feel any adaptive benefits unless the water is 50F.

      That said, I’m in for 6-7 minutes, not long enough to drop my core below 95F (the danger point). Unfortunately, my water temp is rising as the warm season approaches, and I am thinking about cold baths. So that leaves me wondering if there is a good way to keep an eye on my core temp.

      Too many people are likely to get hurt/dead if this trend isn’t made more safe with proper caveats by those endorsing it. More effort needs to be made to identify safe technique, and not just “listen to your body”.

      Other than tolerating cold better, there is no clear evidence this will produce any benefits for your health.

      Even worse, you have people like Jack Kruse making preposterous claims, and personally I find the comments on his blog scary. He should be seen as someone who needs to be monitored, not idolized.

  24. claudia rowe

    Some personal experience, in case it’s of any interest: I am insulin senstive but leptin resistant so, as you contend, it’s quite possible. I followed the Dr Kruse Leptin Rx for 6 months and my serum leptin levels rose every month for that six months. My insulin levels remained about the same.

    The Leptin Rx didn’t achieve what I was hoping for because, as Dr Kruse maintained, of “inflammation” however, IL-6, TPOs, lupus antibodies, et al all remained about the same and within normal range.

    I also wondered about why the 50g+ of protein each morning, and its advantage or purpose, but could not really get to the heart of these recommendations from Dr Kruse.

  25. George

    Great article Todd,

    Once more. I have seen Wim and i am about to buy the book.
    To my eyes he is a genuine person that seeks to spread will power across the globe.
    However, I do have a logical question that i can not answer; during winter times the heart attacks (as well as other ‘ailments’) are hugely higher than in summer. I have actual examples from friends and family. Most doctors refer to lower temperatures and blod clots. Shouldn’t we for the same purpose look for warmer climate with more sun exposure? Isn’t this an oxymoron to look for cold adaptation and at the same time be healthier in warmer environments?

    Thank you


    • Todd


      Most of Wim’s feats are focused on adaptation to the cold, but my understanding is that he has also worked on adaptation to extreme heat; for example running long distances in the desert. I think there is value to improving our adaptation to BOTH hot and cold, or for that matter to other stresses such as going without food for most of the day, adaptation to strenuous exercise, and the like. It is important to be reasonable, and know how far one can push the adaptation. This requires some skill in listening to your body, and detecting the “edge” of adaptation. You should only push as hard as your state of health can tolerate.



  26. king of the monkey bars


    I tried the cold shower for the first time a couple of days ago and I’m still among the living, although it was touch and go for the 30 seconds I lasted. I will keep trying. On your thoughts concerning extreme heat and cold: for my entire work life I’ve labored either in very harsh weather or inside of very hot factories. For the last 15 years I’ve worked in a commercial bakery that is routinely 100 degrees, and during the summer months can get to 120 degrees for days at a time. I thought I’d die the first week but have adapted well. I have always favored cool or cold weather. I feel hot most of the time and my family is always complaining when I open doors and windows on cold days, or drive with the windows down. I truly believe heat and cold tolerance are different sides of the same coin. As you say, colds and flu are a very rare occurrence to me, and I believe it is directly related to adapting to extreme conditions. As I am past 60, I am very interested in any therapies that will enhance my body’s resistance to the ravages of old age, which makes me happy I stumbled upon your site.

  27. Oliver

    Hi Todd,

    Couple questions if you don’t mind

    1. Do you use cold water therapy as much in the winter onths as you in the summer months?

    2. Also how has the more extreme cold water experiments going? do you still do them? Or do you find standard cold water theropy is good enouhg?

    • Todd


      I experimented with cold baths for several months last year. I would soak in an ice cold bath for 20 minutes. Eventually, I came to the conclusion that a 5 minute cold shower is more effective for me than a 20 minute cold bath. The shower involves constant convective heat transfer, because the water is moving. If you lay still in a bath, the water next to your skin forms a warm “boundary layer” so you have to keep paddling to induce heat transfer. I find the showers are a much more efficient and quick way to fit cold exposure into a daily routine.

      I take cold showers all year long. The cold water in my water tank is definitely colder in the winter, and comes it at around 50-55 F (10-13 C). I think cold exposure is especially important in the winter. I find that the cold water induced thermogenesis actually warms me up (after I step out of the shower), and seems to inoculate me against catching a cold or flu.


      • Oliver

        ah ha, interesting points about about static ice baths and movement of the water during a shower! Also anther good point about cold water in the winter in order to keep the cold away. Aweome insights. Thank you. Do you know if there is any connection between particular hormones and cold water therapy? Such as the rise or full in testosterone levels, insulin, growth hormone?

        • Todd

          I’m not aware of any connection between cold water exposure and changes in hormonal balance. Perhaps we should both research this.

  28. Christopher Brown

    Art De Vany has a balanced discussion of cold exposure, but he comes down against cold showers and baths because of the elevation of blood sugar induced, he likes just some cold water on the legs instead.

    I would be interested in Todd’s opinion on this.

    there do seem to be some caveats to the degree to which we should use cold exposure as a health or body composition intervention.

    Plunging into an ice bath will raise your blood sugar, promote urination, and constrict your blood vessels. If you already have occluded blood vessels, this may not be the safest thing to do.

    Even a very cold shower may promote a similar response. I recommend just running cool water over your legs or mild cold exposure such as a brisk walk in the early, cool morning. Or, my favorite, a motorcycle ride that induces some shivering.

    On the positive side, the adaptations that we carry to cold exposure are there for our benefit, but we suffer the collateral damage of not using them. So, protective mechanisms may turn into deleterious ones if they are no longer used. Shivering now and then and burning energy in our brown adipose tissues (BAT) does good things. BAT thermogenesis relieves our mitochondria of ROS damage and alters gene expression so we produce more BAT and less SAT (subcutaneous adipose tissue).

    Cold exposure and exercise have similar metabolic effects; they increase leptin, GH and BDNF and deplete SAT. I personally like to work out in the cold or at least at cool temperatures.

    Cold exposure and exercise alter the hormonal profile in similar ways, all to the good. They are both profoundly anti-inflammatory, which is a good thing. Inflammation is rampant in the over-fed, under-exercised, and SAT is a primary locus for low-grade inflammation that damages us in insidious ways.

  29. charles

    Life use to be extremely hard. As such the human body can do remarkable things. Today’s plush life style has caused people to no longer display these remarkable feats of hardiness however the human body is still more than capable of preforming them with the right conditioning.

    I wish more people were like Wim and developed their natural physical abilities. It is a wonderful thing being in tune with your body and experiencing your life at full physical potential.

  30. Super interesting!! It sounds invigorating being able to come out of such cold/sensation experience. I wish I could do ice baths but unfortunately live on a sailboat and water and ice is extremely precious! 🙂 Maybe will try it in when I visit the states!

  31. I see that this article is from 2012 but it is still a really great read. I am also really passionate about health and cold exposure has been a real blessing for me since 2009 when I first in India and they didn’t have hot water. I was taking cold showers every day and I never looked back! 🙂

    I think you would definitely be be interested to check out if you haven’t already heard about it. Wim Hof now has an online training course called The Wim Hof Method It’s 10 weeks go at your own pace video modules, includes access to a group forum so you can share your progress with others and you can ask Wim and his support team questions at any time. It’s really fun and shows you how to do what Wim does.

    Everyday, I am amazed at the stories that people are sharing about their experiences. Just wanted to share! Thanks for the article. Blessings friend! 🙂

  32. Hello, I would expect that the Wim Hof Method is based mainly on the meditation and mind training. I cannoti imagine how this could be managed by reading or watching a video. Could you write more on that? Thank you, Pavel, Czech Republic.

    • Todd

      You are most definitely correct that reading and watching videos won’t magically endow you with the ability to tolerate the cold, hold your breath, or lower your heart rate. All of this requires training. Some of the training involves “Tummo” or meditative training. But ultimately, there is no shying away from the cold hard fact that to build tolerance to a stressor, you need to progressively expose yourself to that stressor — whether it be cold or hot water, or anything else. I suggest reading Justin Rosales’s book, “Becoming the Iceman” to get a sense of what this training involves.

  33. Summer

    Did you ever do a follow up post about how the rest of the cold baths went? Do you still do them or did you go back to showers.

    I’m on day 9 of cold showers twice a day. I first read about them in the 4HB.

    Anyway, I’m loving your site. I’ve learned about lots of things I didn’t know I was missing out on. Thank you!

    • Todd

      Sorry, I did not follow up on the experiments. I continue to take cold showers every morning, though!

  34. Hi Todd, Did you continue the experiment? Any follow up comments.

    • Todd

      Hi Peter,

      No. Oliver asked the same question on June 5, 2013. Here was my reply, which I think still holds:


      I experimented with cold baths for several months last year. I would soak in an ice cold bath for 20 minutes. Eventually, I came to the conclusion that a 5 minute cold shower is more effective for me than a 20 minute cold bath. The shower involves constant convective heat transfer, because the water is moving. If you lay still in a bath, the water next to your skin forms a warm “boundary layer” so you have to keep paddling to induce heat transfer. I find the showers are a much more efficient and quick way to fit cold exposure into a daily routine.

      I take cold showers all year long. The cold water in my water tank is definitely colder in the winter, and comes it at around 50-55 F (10-13 C). I think cold exposure is especially important in the winter. I find that the cold water induced thermogenesis actually warms me up (after I step out of the shower), and seems to inoculate me against catching a cold or flu.



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