Huberman LabHow to Use Cold & Heat Exposure to Improve Your Health | Dr. Susanna Søberg
CHAPTERS
- 0:00 – 5:40
Introduction to Dr. Søberg and the Science of Cold and Heat
Huberman introduces Dr. Susanna Søberg, outlining her background in metabolism research and her seminal 2021 Cell Reports Medicine paper on cold and heat thresholds for brown fat activation. He previews the episode’s focus: practical, science-based protocols for deliberate cold and heat exposure and their impact on metabolism, hormones, and neurotransmitters.
- 5:40 – 14:40
Sponsors and Live Tour Announcements
Huberman pauses for sponsor messages and to announce live Brain-Body Contract events. This segment is unrelated to the core scientific discussion but frames the podcast’s funding model and outreach activities.
- 14:40 – 23:20
What Happens During Cold Shock? Physiology and Psychology
Søberg explains what occurs when someone enters uncomfortably cold water—whether via open water, cold plunge, or shower. They detail the cold shock response, sympathetic activation, catecholamine release, breathing changes, and how adaptation blunts the shock over time.
- 23:20 – 33:20
Discomfort, Adaptation, and Individual Differences in Cold Tolerance
They discuss why some people seem to tolerate cold easily while others dread it, even among elite performers such as special operations soldiers. Søberg notes nervous system sensitivity, avoidance behavior, and cold pain perception, and emphasizes that adaptation reduces distress over time.
- 33:20 – 41:40
Cold Showers vs. Full Immersion vs. Ambient Cold
The discussion compares different cold-exposure modalities: outdoor cold air, cold showers, partial immersion, and full-body submersion. Søberg explains how coverage of skin with cold water strongly affects receptor activation and brown fat stimulation, and why cold-shower research lags behind immersion studies.
- 41:40 – 50:20
How Cold Signals Reach and Activate Brown Fat
Søberg outlines the three main pathways linking skin-cold sensing to brown fat activation. She explains hypothalamic integration, direct skin-to-BAT innervation, and muscle-shiver signaling, highlighting evolutionary redundancy for thermoregulation.
- 50:20 – 1:00:00
Shivering, Afterdrop, and Why Shiver Is Beneficial
They delve into shivering thermogenesis and the ‘afterdrop’ phenomenon: why core temperature continues to fall after leaving cold water. Søberg argues shiver should not be feared—it’s a sign of metabolic training—and she explains how afterdrop arises from reperfusion of cold peripheral blood.
- 1:00:00 – 1:09:10
Hormetic Stress: Why Cold and Heat Are Like Exercise
Huberman and Søberg parallel cold/heat stress with exercise-stress, emphasizing that transient, high-strain states (inflammation, high blood pressure, etc.) are necessary to produce long-term healthful adaptations. They also introduce the concept of cellular hormesis via heat-shock and cold-shock proteins.
- 1:09:10 – 1:18:20
Long-Term Adaptations: Insulin Sensitivity, Blood Pressure, and Season-Long Change
Søberg reviews prior winter-swimming cohort data showing that a full winter season improves metabolic and cardiovascular markers. They relate this to her own controlled study and the broader concept of using cold for prevention of lifestyle diseases.
- 1:18:20 – 1:30:00
Deep Dive Into Brown Fat: Biology, Location, and Plasticity
They explore what brown fat is, where it resides, and how it changes with age, obesity, and chronic catecholamine exposure. Søberg highlights PET imaging data, cancer case evidence for BAT plasticity, and age-related loss linked to obesity.
- 1:30:00 – 1:41:40
Environmental and Lifestyle Drivers of Brown Fat: Cold Rooms, Outdoor Work, and NEAT
Søberg discusses studies where mild chronic cold exposure—like sleeping at 19°C—grew brown fat and improved insulin sensitivity in just one month. Huberman adds anecdotal and classic physiology data on non-exercise activity and cold labs, reinforcing the role of daily environment.
- 1:41:40 – 1:50:00
Scandinavian Culture: Seasonal Acclimation, Babies Sleeping Outside, and Winter Swimming
They explore traditional Nordic practices that incidentally train thermoregulation: underdressing before winter, overdressing before summer, and putting babies to nap outdoors. Observations from Copenhagen highlight widespread, age-spanning use of cold water.
- 1:50:00 – 2:00:00
Designing the Søberg Winter Swimmer Study
Søberg explains how she designed her human BAT study: observational rather than interventional, with experienced winter swimmers and matched controls. She describes recruitment, matching criteria, and why she initially used only male participants.
- 2:00:00 – 2:08:20
The Winter Swimming plus Sauna Protocol: Frequencies, Durations, Temperatures
She details the actual protocol winter swimmers were habitually using: frequency of visits, cold-immersion duration, sauna duration, and the order of exposure. This real-world pattern became the basis for deriving weekly ‘minimum effective dose’ thresholds.
- 2:08:20 – 2:16:40
Key Outcomes: Brown Fat Activation, Insulin Sensitivity, and Glucose Handling
Using PET/MRI scans, thermography, and metabolic testing, Søberg found winter swimmers had more active brown fat, used less insulin to control blood sugar, and cleared glucose from the bloodstream faster than controls, even when fasting and at rest.
- 2:16:40 – 2:23:20
Thermal Comfort Differences, Sex Differences, and Why Only Men Were Studied
They touch on known thermal and BAT differences between men and women, explaining why the initial study focused on men. Huberman and Søberg discuss comfort temperatures and surface temperature differences across sexes.
- 2:23:20 – 2:31:40
Diving Reflex, Face Dunking, and Head-Under Considerations
They discuss the mammalian diving reflex and whether immersing the head or face changes the physiological profile of cold exposure. Søberg cautions about additional heat loss and potential dizziness when submerging the head.
- 2:31:40 – 2:40:00
Why End on Cold: The Søberg Principle
Søberg articulates the logic behind her recommendation to finish sessions with cold: doing so forces your body to self-reheat, keeping brown fat and muscles working for hours afterward and extending hormonal and metabolic benefits.
- 2:40:00 – 2:50:00
Practical Adaptation: Frequency, Bout Structure, and Temperature Variation
They translate the research into pragmatic advice: how to reach ~11 minutes/week of cold and ~57 minutes/week of heat, why multiple short bouts are superior to one long one, and why varying temperatures keeps the system adaptive.
- 2:50:00 – 3:00:00
Safety and Special Populations: Kids, Small Bodies, Raynaud’s, and Extremity Pain
The conversation turns to safety: hypothermia risk in children and smaller adults, strategies for managing hand/foot pain, and the lack of rigorous studies on conditions like Raynaud’s and autoimmune disease in relation to cold exposure.
- 3:00:00 – 3:06:40
Social Norms, Skinny Dipping, and Scandinavian Sauna Culture
They briefly discuss clothing-optional winter swimming and sauna traditions in Denmark, clarifying that nudity offers no physiological advantage—only psychological and cultural dimensions. Huberman notes similar practices in Russian banyas.
- 3:06:40 – 3:15:00
Outlier Case: A Winter Swimmer With No Measurable Brown Fat
Søberg recounts one remarkable subject: an experienced winter swimmer who had no detectable brown fat on PET/MRI. His responses during cooling experiments resembled controls, and he shivered more vigorously and earlier than other swimmers.
- 3:15:00 – 3:25:00
Inflammation, Mental Health, and Future Research Directions
Søberg discusses inflammatory markers (IL-6, IL-10) and their potential link to reduced chronic inflammation and mental health benefits. She highlights gaps: sleep, mood, autoimmune conditions, and a forthcoming study including both men and women.
- 3:25:00
Closing Reflections and Resources
Huberman thanks Søberg and underscores the importance of rigorous yet accessible work on cold and heat exposure. He directs listeners to her book and institute, mentions the Huberman Lab newsletter and social channels, and reiterates the role of science-based tools in everyday life.
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