What are the differences between various cold exposure methods like showers, ice baths, and cold air?

More skin coverage by cold water (like in an ice bath) leads to stronger activation of cold receptors and the autonomic nervous system compared to standing in a cold wind. However, even exposure of extremities like hands can activate brown fat. Different methods offer varying degrees of stimulus.

How does the body activate brown fat in response to cold?

Cold receptors in the skin send signals to the brain's temperature regulation center (hypothalamus). This triggers neurotransmitters like norepinephrine, which directly activate brown fat. There are also direct pathways from skin receptors and even muscles to brown fat.

What is the 'post-exposure drop' and how does shivering relate to it?

After exiting cold water, blood vessels constrict to conserve core heat. When they re-open to release warm blood to the surface, this cooled blood lowers core body temperature, leading to shivering. Shivering itself helps reactivate brown fat and reheat the body.

How does cold exposure improve metabolic health and insulin sensitivity?

Cold exposure activates brown fat, which increases metabolism. It also stimulates mitochondria in brown fat cells to burn glucose and fatty acids. Studies show winter swimmers have improved insulin sensitivity and faster glucose clearance from the blood.

What is the minimum effective dose of cold and heat exposure per week?

Research suggests around 11 minutes of cold exposure and 57 minutes of sauna exposure per week can be effective. This can be broken down into 1-2 minute cold plunges and 10-15 minute sauna sessions done 2-3 times a week.

Can cold and heat exposure help reduce inflammation and prevent chronic diseases?

Yes, studies show that cold and heat exposure can reduce inflammation markers like Interleukin-6. This reduction in inflammation is linked to a lower risk of lifestyle diseases such as Type 2 diabetes and mental health conditions like depression and anxiety.

Is it better to have prolonged cold exposure or frequent, shorter exposures with temperature changes?

Temperature variability and cycling between hot and cold are key. It's not just about feeling cold, but the transition. Frequent, shorter exposures and returning to a warmer state (the 'Søberg Principle') can strengthen cells and boost metabolism, making the body more resilient.

Key Moments

Essentials: Cold & Heat Exposure for Metabolic Health | Dr. Susanna Søberg

Andrew Huberman

Science & Technology6 min read39 min video

Nov 5, 2026|45,300 views|376|62

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Key Moments

TL;DR

Deliberate cold exposure activates brown fat to boost metabolism and insulin sensitivity, but the intensity and duration are more flexible than commonly believed.

Key Insights

Cold exposure, particularly immersion in cold water, strongly activates brown adipose tissue (BAT) which increases metabolic rate.

Shivering, a byproduct of cold exposure, stimulates BAT and contributes to thermogenesis, enhancing metabolic health.

Consistent cold and heat exposure, as little as 11 minutes of cold water and 57 minutes of sauna per week, can significantly improve insulin sensitivity.

Winter swimmers showed increased insulin sensitivity and faster glucose clearance compared to a control group, with only 1-2 minutes in cold water per session.

The 'Søberg principle' suggests ending cold exposure by allowing the body to rewarm itself, which sustains metabolic and neural activity for hours.

A 19°C (66°F) sleeping environment for one month was shown to increase brown fat and improve insulin sensitivity in a study by Hansen et al. (2017).

Understanding the cold shock response and metabolic activation

Dr. Susanna Søberg explains that deliberate cold exposure, such as immersing oneself in cold water, triggers the 'cold shock response.' This involves the sympathetic nervous system and catecholamines, leading to increased respiration. While initial exposure can cause over-breathing and a gasp reflex, adaptation over time reduces this intensity, building resilience. The key is to reach a point of 'uncomfortable cold,' which signals sufficient stimulation. Cold exposure, particularly full immersion where more of the body is exposed to cold water, leads to a stronger activation of cold receptors in the skin, resulting in a more robust autonomous nervous system response. This enhances norepinephrine and activates brown adipose tissue (BAT), a healthy fat that increases metabolism.

Brown fat: The body's internal furnace

Brown adipose tissue (BAT) is a specialized type of fat that plays a crucial role in thermogenesis, helping to maintain body temperature. Cold exposure is a primary activator of BAT. When skin's cold receptors detect a drop in temperature, they send signals to the hypothalamus in the brain. This leads to rapid increases in neurotransmitters like norepinephrine and adrenaline. Norepinephrine then directly activates BAT, initiating heat production. There's also a direct pathway from skin receptors to BAT and a third pathway involving muscle shivering, which also contributes to thermogenesis. This intricate system ensures the body stays warm and maintains homeostasis, highlighting BAT's importance in regulating body temperature and metabolic health.

Shivering and its metabolic benefits

Shivering, while uncomfortable, is a vital part of the body's response to cold. It's a secondary mechanism for increasing heat production, following the activation of brown fat. The phenomenon known as 'afterdrop,' where core body temperature continues to fall even after exiting cold water, is linked to the rewarming of peripheral blood. As blood vessels dilate upon exiting the cold, warm blood from the core flows to the cooler extremities, cools down, and returns to the core, lowering overall core temperature. This drop can then trigger shivering. Far from being something to fear, shivering is seen as a form of exercise for your cells, akin to a workout at the gym. It induces 'hormesis,' a beneficial stress response that strengthens cells. Similar to how exercise increases heat shock proteins in muscle cells, cold exposure increases cold shock proteins, making cells more resilient and improving their function. This cellular training enhances metabolic health and insulin sensitivity.

Metabolic adaptations and long-term benefits of cold exposure

Consistent exposure to cold leads to metabolic adaptations that improve overall health. As individuals adapt, their brown fat becomes more active, with more numerous and efficient mitochondria, enhancing their thermogenic capacity. The body also becomes better at constricting blood vessels in the skin, providing a better 'shield' against the cold. Stress response systems become more finely tuned, leading to a reduced release of catecholamines during subsequent exposures. Crucially, this metabolic boost leads to improved insulin sensitivity. A study by Sundevall et al. (2016) observed winter swimmers over four to five months, noting reduced blood pressure, lower heart rate, and improved insulin sensitivity. These long-term effects, including better glucose balance and reduced inflammation, highlight the preventative potential of cold exposure against lifestyle diseases.

Activating brown fat without extreme cold

While cold immersion is potent, brown fat can be activated through less extreme methods. Simply exposing a hand to cold water has been shown to activate BAT. Studies suggest that individuals with higher levels of physical activity or those who frequently change body temperature tend to have more BAT. Even mild interventions like wearing light clothing in cold air or using cooling vests for 10 days can increase BAT. Crucially, sleeping in a cool environment, around 19°C (66°F), has also been proven effective. A study by Hansen et al. (2017) found that after one month of sleeping at 19°C, participants showed increased BAT and improved insulin sensitivity. Conversely, sleeping in warmer temperatures (24°C and 27°C) led to a decrease in BAT activation and insulin sensitivity, underscoring the significant impact of ambient temperature on metabolic health.

The synergistic effects of cold and heat therapy

Dr. Søberg's research explored the combined effects of cold and heat exposure, particularly focusing on winter swimmers who engaged in both cold water plunges and sauna sessions. These individuals were found to have significantly increased insulin sensitivity and produced less insulin when fasting compared to a control group. They also exhibited a faster clearance of glucose from their bloodstream after consuming a glucose drink. The total weekly commitment for these benefits was surprisingly low: approximately 1-2 minutes in cold water and 10-15 minutes in a sauna per session, totaling around 11 minutes of cold and 57 minutes of sauna per week. This suggests that consistent, moderate exposure to both temperature extremes can yield substantial metabolic improvements, including enhanced glucose metabolism and reduced inflammation.

The 'Søberg Principle': Ending cold exposure with rewarming

A key takeaway from Dr. Søberg's work is the 'Søberg Principle,' which emphasizes ending cold exposure in a way that forces the body to rewarm itself. This self-warming process, triggered by the body's natural thermogenic mechanisms (BAT and muscles), extends the metabolic benefits for hours post-exposure. It's akin to continuing a workout after leaving the gym. This prolonged metabolic activity not only aids in fat burning but also keeps neurotransmitters active, which are crucial for continued BAT stimulation. Repeatedly challenging the body with temperature fluctuations, rather than just prolonged single exposures, strengthens cells and increases their adaptability. Winter swimmers, for instance, were observed to have warmer skin temperatures and increased BAT activity even when resting, indicating a sustained thermogenic state.

Reducing inflammation and its implications for chronic disease

Beyond metabolic markers, cold and heat exposure show promise in reducing inflammation. Studies have measured inflammatory markers like Interleukin-6 and Interleukin-10, finding that these exposures can help lower them. This anti-inflammatory effect is critical, as chronic inflammation is linked to a wide range of modern lifestyle diseases, including type 2 diabetes, depression, anxiety, and Alzheimer's disease. By leveraging natural stressors like temperature changes, the body can be reset to a more balanced, homeostatic state, promoting self-repair. This approach offers a potent, accessible method for disease prevention and management, countering the effects of a modern, sedentary lifestyle that has distanced us from natural temperature variations. The key is not extreme temperatures, but consistent, varied exposure to thermal stress.

Mentioned in This Episode

●Supplements

●Products

●Companies

●Studies Cited

●Concepts

●People Referenced

Cold and Heat Exposure Quick Guide

Practical takeaways from this episode

Do This

Aim for an uncomfortable level of cold to activate the sympathetic nervous system and catecholamines.

Understand that shivering is a natural response that helps reheat the body and can activate brown fat.

Focus on temperature variability (warm to cold, cold to warm) for greater benefits.

Start with shorter durations and less extreme temperatures, gradually increasing.

Consider sleeping in a cooler room (around 19°C) to activate brown fat.

End cold exposure by allowing the body to reheat itself to continue metabolic benefits.

Engage in regular, shorter cold/heat exposures (e.g., 1-2 min cold, 10-15 min sauna, totaling 11 min cold and 57 min sauna per week) for adaptive stress.

Be aware that cold and heat exposure can reduce inflammation, potentially benefiting conditions like Type 2 diabetes, depression, anxiety, and Alzheimer's.

Avoid This

Do not avoid the initial discomfort or 'cold shock' as it indicates activation of key physiological systems.

Do not fear shivering, as it is a crucial part of the body's rewarming process.

Do not aim for enjoyment during cold exposure; it should be challenging.

Avoid excessively long or extreme cold exposure that leads to dangerous hypothermia.

Do not assume extreme cold temperatures (like ice baths constantly) are necessary for brown fat activation; moderate cold and temperature changes are effective.

Avoid excessive heat or cold exposure, as this can exhaust cells and increase cardiovascular risk.

Common Questions

You should reach a level of uncomfortable coldness, which triggers a 'cold shock' response. This involves hyperventilation and activation of the sympathetic nervous system and catecholamines. The goal is not comfort, but a challenging stimulus.

Topics

Autonomic Nervous System Metabolic Health Cold Exposure Health & Longevity Neuroscience & the Brain Human Performance Insulin Sensitivity Heat Exposure Brown Fat Activation

Mentioned in this video

Studies & Research

Hansen et al. 2017

A study that showed sleeping at 19°C for a month increased insulin sensitivity and brown fat activation.

Supplements

Calcium HMB

An ingredient added to AG1 Pro, known to support muscle recovery.

Omega-3 Co-Enzyme Q10

A free gift with the first AG1 subscription.

Yerba mate

A fermented drink known for providing energy without jitters and other health benefits.

Zinc Carnosine

An ingredient added to AG1 Pro, known to support gut lining.

Creatine monohydrate

An ingredient added to AG1 Pro, known to support muscle strength and brain health.

Products

Pod 6

The latest and most advanced sleep system from Eight Sleep.

AG1

A nutritional supplement that combines vitamins, minerals, probiotics, and adaptogens.

AG1 Pro

The latest formulation of AG1, adding creatine, HMB, and zinc carnosine.

Matina

Company that makes a fermented, sugar-free yerba mate drink.

People

Wim Hof

Mentioned in the context of discussing the 'post-exposure drop' phenomenon.

Susanna Søberg

Guest expert on cold and heat exposure, metabolic health, and brown fat.

Andrew Huberman

Host of the Huberman Lab podcast, discussing cold and heat exposure.

Concepts

Interleukin-10

An anti-inflammatory marker that followed the increase of Interleukin-6 in Søberg's study.

Interleukin-6

An inflammatory marker measured in Søberg's study; it increased, followed by Interleukin-10.

Companies

Eight Sleep

Company that produces smart mattress covers for cooling and heating, and sleep tracking.

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