Huberman LabHow to Use Cold & Heat Exposure to Improve Your Health | Dr. Susanna Søberg
At a glance
WHAT IT’S REALLY ABOUT
Cold And Heat: Simple Weekly Habits To Supercharge Metabolism, Mood
- Andrew Huberman interviews Dr. Susanna Søberg about how deliberate cold and heat exposure reshape metabolism, brown fat activity, cardiovascular health, and brain chemistry. Drawing from her 2021 Cell Reports Medicine study and related work, Søberg explains how brief, uncomfortable temperature stress drives powerful hormetic adaptations. They outline practical thresholds—about 11 minutes of cold and 57 minutes of sauna per week—that improve insulin sensitivity, blood pressure, brown fat function, and resilience to cold. The conversation also covers mechanisms (sympathetic activation, catecholamines, brown fat pathways), safe protocols, individual differences, and why ending on cold (the “Søberg Principle”) extends the metabolic benefits for hours afterward.
IDEAS WORTH REMEMBERING
5 ideasYou Need Surprisingly Little Cold and Heat to Get Big Benefits
In Søberg’s winter-swimmer study, participants averaged a total of ~11 minutes of cold-water immersion and ~57 minutes of sauna per week, split across 2–3 sessions (each session: 1–2 minutes in 2–12°C water, then 10–15 minutes at ~80°C sauna, repeated three cold dips and two sauna bouts, ending on cold). Even at this relatively low dose, winter swimmers showed significantly better insulin sensitivity, lower insulin secretion, lower blood pressure, and improved glucose clearance compared to matched controls. This indicates that brief, consistent exposure—not extreme or prolonged sessions—is sufficient to drive measurable health gains.
The Goal Is Discomfort and Contrast, Not Extreme Temperatures
Cold and heat act as hormetic stressors: mild, time-limited challenges that trigger adaptive responses. For cold, the key is that it feels uncomfortably cold and elicits a short-lived cold shock (gasp, rapid breathing, strong sympathetic activation), not that it reaches some arbitrary ultra-low temperature. Similarly, data from Finnish sauna cohorts suggest cardiovascular benefit rises with session length up to about 19–30 minutes, but more than that adds little or may become counterproductive. Varying temperature and using multiple short bouts (cold–warm–cold) keeps the system responsive without overtaxing it.
Brown Fat Is Plastic, Trainable, and Central to Metabolic Health
Brown adipose tissue (BAT) is a mitochondria-dense, thermogenic fat depot located mainly in the supraclavicular region, along the spine, and near large vessels. It’s activated by skin-cold-triggered sympathetic output (norepinephrine), direct skin-to-BAT neural pathways, and signals from shivering muscles. Ten to thirty days of mild cold (e.g., 19°C sleeping environments, cooling vests, outdoor exposure) can measurably increase BAT volume and activity, improving insulin sensitivity and enhancing clearance of glucose and fatty acids from the bloodstream. People who habitually work outdoors tend to retain more BAT with age.
Ending on Cold Extends Thermogenic and Neurochemical Benefits
After cold immersion, blood vessels constricted in the cold reopen, leading to an ‘afterdrop’—core temperature continues to fall briefly as cooled blood returns from the periphery. If you end on cold and then re-warm naturally (without a hot shower or sauna), your brown fat and muscles must ramp up thermogenesis for hours to restore core temperature. This prolongs elevated metabolism and catecholamine activity beyond the immersion itself. The “Søberg Principle” is to structure sessions so you finish with cold, then layer up and move around to let your body do the heating work.
Cold Exposure Rapidly Boosts Catecholamines and Can Improve Mood
Immersion up to the neck in cold water triggers a strong sympathetic response: heart rate and blood pressure spike, and catecholamines (norepinephrine, epinephrine, dopamine) surge in the brain and body. With adaptation, the hyperventilatory shock attenuates while mood-enhancing and alertness-promoting neurochemistry remains robust for hours afterward. Repeated exposures also appear to increase resilience to stress more generally, with winter swimmers often reporting better baseline mood, more energy, and improved sleep—though formal mood and sleep measures still need more controlled study.
WORDS WORTH SAVING
5 quotesAs long as you get uncomfortably cold, it's cold enough.
— Dr. Susanna Søberg
You shouldn’t think about cold water immersion as something that is comfortable. It should be hard, because that’s the point of it.
— Dr. Susanna Søberg
Brown fat is like your first responder in the body to keep your temperature up.
— Dr. Susanna Søberg
If you end on the cold, you have an exercise for your body going on for hours afterwards.
— Dr. Susanna Søberg
We don’t need extreme exposure. We need brief, repeated exposure to different temperatures to keep our cells on their toes.
— Dr. Susanna Søberg
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