Wim Hof Method
Wim Hof Method · Breath, Cold & Commitment
Evidence grade 2 of 5, Thin. Read how the Atlas grades evidence.
8 human trials, about 9 studies, Roughly 15 to 48 subjects per trial; mostly young healthy men (about 86% male). The written rationale for this grade is still being prepared.
- FDA
- Not an FDA-regulated product; no drug or device clearance. Marketed as wellness training, not medical treatment.
- WADA
- Breathing and cold exposure are not WADA-prohibited; no banned substances involved in the method itself.
Reference only. Not medical advice.
What can go wrong
Safety comes first here, ahead of any benefit. The breathing technique is voluntary hyperventilation, which drops blood carbon dioxide (hypocapnia) and can make you faint with no warning and no feeling of breathlessness beforehand. Never do the breathing in or near water of any kind, including a bath, pool, lake, ocean or shower, and never while driving or standing; hyperventilation followed by breath-holding causes shallow-water blackout, and press investigations and Hof's own warnings link the technique to drowning deaths. Always practice seated or lying on a soft surface where a sudden faint cannot hurt you. This is not appropriate self-care for eating, mood or panic problems; if you are using it to manage anxiety, panic or low mood, please work with a qualified clinician rather than relying on the breathing. Avoid the breathing entirely if you are pregnant, have epilepsy or a seizure history, serious heart disease, uncontrolled high blood pressure, or a history of fainting. Cold immersion adds separate risks of cold shock and heart-rhythm disturbance. Anyone with a heart, lung, neurological or psychiatric condition should talk to a clinician before starting, and stop and seek care for chest pain, severe dizziness or palpitations.
The marquee study is Kox et al. 2014 in PNAS. Twelve men trained in cyclic hyperventilation, breath holds and cold exposure, and twelve untrained controls, were injected with a bacterial endotoxin. The trained group showed a sharp rise in adrenaline, higher anti-inflammatory interleukin-10 (up 194 percent), a blunted pro-inflammatory response (TNF-alpha, IL-6 and IL-8 down roughly half), and 56 percent fewer flu-like symptoms. It is a genuine peer-reviewed result, but it involved 24 healthy men and an acute lab challenge, not any disease outcome. Follow-up work fills in mechanism. Muzik et al. 2018 in NeuroImage imaged Hof and reported that brown-fat activation was unremarkable, pointing to brain and central nervous system control rather than fat-driven heating. Zwaag et al. 2022 at Radboud tied the breathing to intermittent respiratory alkalosis and brief hypoxia that drive the catecholamine surge, and found the effect did not require Hof himself as the teacher. The only systematic review, Almahayni and Hammond 2024 in PLOS One, covered 9 papers and 8 trials and judged every trial at high or very high risk of bias, with small, mostly male samples. So the honest read is narrow. The acute adrenaline and anti-inflammatory signal is real and has been replicated; claims about treating autoimmune disease, depression or aging are not established. The most serious caveat is safety, not efficacy. The breathing lowers carbon dioxide enough that a person can pass out with no warning, and combined with water this can cause shallow-water blackout and drowning.
Cyclic over-breathing, breath holds and cold exposure. One real immune study; most claims still outrun the evidence
What people take it for
These are the reasons people give for taking it. They are not effects it has been shown to have.
What people get wrong
Often saidThe method proves you can consciously control your immune system to fight disease.
ActuallyKox et al. 2014 showed a short-term blunted inflammatory response to injected endotoxin in 24 healthy men, an acute lab challenge and not treatment of any illness; the 2024 PLOS One review of 8 trials rated them all at high or very high risk of bias.
Often saidThe breathing is safe to do anywhere, including in water.
ActuallyHyperventilation followed by breath-holding can cause loss of consciousness with no air-hunger warning, which in water is shallow-water blackout; Hof's own materials warn against practicing near water for exactly this reason.
Often saidCold exposure works mainly by firing up brown fat to burn calories.
ActuallyMuzik et al. 2018 imaging described brown-fat activation as unremarkable and concluded that brain and central nervous system control, not peripheral fat, primarily drove Hof's cold response.
Often saidA short course lets you match Wim Hof's own extreme feats.
ActuallyThe trials involved trained volunteers doing controlled tasks; the ice-endurance records are Hof's personal claims, and the review found no evidence that brief training confers unusual cold survival.
Who profits, and who pushes back
Omar Almahayni and Lucy Hammond, 2024
Findings are promising, but every trial carried a high or very high risk of bias, with small and mostly male samples, no pre-registered protocols, and no feasible blinding; more robust confirmatory research is needed before the method can be recommended for health outcomes.
Scott Carney
The breathing and the water are each safe alone, but conflated they add up to an efficient way to drown; by January 2024 he counted 21 deaths and 18 injuries he had linked to practitioners, and argues the safety risk is downplayed relative to the marketing.
Wim Hof / Innerfire BV
Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.
Sells courses, app subscriptions and instructor certification; commercial interest in the method.
Certified WHM instructors
Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.
Pay for and earn from certification; financially tied to the brand.
Matthijs Kox and Peter Pickkers
Academic investigators behind the 2014 PNAS study; not part of the commercial venture.
Otto Muzik
Led independent brain-imaging work on mechanism, not brand-funded.
Where the research comes from
| Place | Share of published research |
|---|---|
| Europe | 42% |
| North America | 34% |
| Asia-Pacific | 14% |
| Latin America | 6% |
| Other | 4% |
Research published from: Netherlands.
How we got here
The cold-and-breath lineage long predates Wim Hof. Tibetan Vajrayana Buddhism developed Tummo (g-tummo), an inner-fire meditation combining breath control and visualization to generate intense bodily heat; it sits among the Six Yogas of Naropa, transmitted from Tilopa (988 to 1069) to Naropa to Marpa, who carried them into Tibet in the 11th century. Indian Pranayama breath-control practices feed the same stream. In 1982 Harvard cardiologist Herbert Benson and colleagues published a study in Nature reporting that three Tummo-practicing monks in the Himalayas could raise finger and toe temperature by as much as 8.3 degrees Celsius and dry cold wet sheets draped over their bodies. Wim Hof, born 20 April 1959 in Sittard, Netherlands, built his own stripped-down secular protocol from cold immersion plus cyclic hyperventilation, set ice-endurance records as The Iceman including 44 minutes in full-body ice contact in 2010, and from a 2011 Radboud University endotoxin experiment onward turned it into a branded global method.
- 11th c.Tummo inner-fire practice transmitted into Tibet via the Six Yogas of Naropa
- 1959Wim Hof born in Sittard, Netherlands
- 1982Benson and colleagues publish a Nature study on Tummo monks raising peripheral body temperature
- 2010Hof sets a record of 44 minutes in full-body contact with ice as The Iceman
- 2011Hof undergoes a Radboud endotoxin test, aired on Dutch television, seeding formal research interest
- 2014Kox and Pickkers publish the PNAS immune-modulation study in 24 healthy men
- 2018Muzik and colleagues report brain imaging pointing to CNS control, with unremarkable brown-fat activation
- 2020Netflix and mainstream coverage drive a surge in popularity
- 2022Zwaag and colleagues detail the respiratory-alkalosis and hypoxia mechanism; the Metzger wrongful-death drowning lawsuit is filed in California
- 2024Almahayni and Hammond systematic review flags high or very high risk of bias across trials; the Metzger case is dismissed and Hof is found not liable
At a glance
- Core loop
- 30 to 40 deep breaths, exhale, hold, then repeat across rounds
- Best-evidenced effect
- Short-term adrenaline rise and dampened inflammatory response
- Hard rule
- Never practice the breathing in or near water (blackout risk)
- Evidence base
- Small, mostly unblinded trials rated high risk of bias
What this entry does not yet cover
What follows is unfinished work on our side, not a finding about Wim Hof Method. A short entry is not a safe entry.
- Cost and market. We have not documented what it sells for or who sells it.
- Supply chain. We have not mapped where it is made.
- Who uses it. We have not documented the user groups.
- What could change. No forward-looking summary yet.
- How it compares. We have not set it against the alternatives.
- Children and teenagers. We have not checked what is known about younger people.
Sources
Kox 2014 PNAS: 24 healthy men (12 trained, 12 control), IV endotoxin, IL-10 +194%, TNF/IL-6/IL-8 down ~half, adrenaline surge
Kox 2014 official record of publication and abstract
Systematic review: 9 papers, 8 trials (5 RCTs, 3 crossover RCTs, 1 cohort), all but one high/very high risk of bias; anti-inflammatory signal promising but uncertain
Systematic review published version and risk-of-bias detail
Muzik 2018: brown-fat activation unremarkable; concluded primacy of CNS over peripheral mechanisms for cold tolerance
Muzik 2018 mechanism, PAG activation, intercostal-muscle heat, brain-over-body conclusion (institutional summary)
Benson 1982 Nature: Tummo monks raised finger/toe temperature and dried wet sheets in a cold room
Tummo lineage, Six Yogas of Naropa, Tilopa-Naropa-Marpa transmission into Tibet
Hof birth 20 April 1959 Sittard; 2010 ice record; 2011 Radboud endotoxin test; Metzger lawsuit filed Dec 2022, dismissed 2 July 2024 with Hof not liable; 32 reported deaths as of March 2024
Scott Carney's death and injury tally (21 deaths, 18 injuries by Jan 2024), shallow-water-blackout mechanism, safety and overclaiming critique
Metzger wrongful-death lawsuit: 17-year-old drowning, negligence and false-advertising claims, $67M sought, injunction request
Almahayni & Hammond review coverage: reduces inflammation, mixed effect on exercise performance, need for robust research