By Dr. Susanna Søberg, PhD · Søberg Institute · soeberginstitute.com
For years, the wellness industry has sold us solutions. Supplements. Devices. Programmes that promise transformation in 30 days or less. And yet the most powerful tools for optimising health, building resilience, and extending longevity have been with us throughout human history — hidden in plain sight in the form of heat and cold.
I am Dr. Susanna Søberg, PhD — a Danish metabolic scientist, international bestselling author, and the founder of the Thermalist® Method and the Søberg Principle. Over more than 15 years of research into human metabolism, thermal physiology, and stress biology, I have studied what cold and heat actually do to the human body at a cellular level. And I have spent the past several years building a system — not just a concept — that translates that science into real-world practice.
This article explains what the Thermalist® Method is, the science it is built on, and how it has evolved from a research finding into a global system now operating in wellness settings across more than 25 countries.
The Science That Started Everything — The Søberg Principle
The Thermalist® Method is built on a specific, peer-reviewed scientific foundation — the Søberg Principle, published in Cell Reports Medicine in October 2021.
The Søberg Principle emerged from research examining how the structure of contrast therapy — the deliberate alternation of cold and heat exposure — influences metabolic outcomes in the human body. Specifically, it established that the sequence in which cold and heat are applied produces measurably different physiological responses.
The publication in Cell Reports Medicine — a peer-reviewed journal from Cell Press, one of the most respected publishers in scientific research — represented a landmark contribution to the scientific understanding of thermal physiology. It was not a study of whether contrast therapy works. It was a study of precisely how it works — and how to structure it for maximum metabolic benefit.
The Søberg Principle has since been discussed on Huberman Lab, referenced in The New York Times, The Times, The Guardian, and BBC Radio, and discussed by Joe Rogan and Andrew Huberman on The Joe Rogan Experience. It is now applied in wellness and hospitality settings across more than 25 countries.
The Søberg Principle is not a wellness trend. It is peer-reviewed science — published, reproducible, and independently evaluated. It is the foundation everything else is built on.
What Is the Thermalist® Method?
The Thermalist® Method is the world's leading science-based contrast therapy system. It is the practical translation of the Søberg Principle and 15 years of research in metabolism, nervous system regulation, and thermal physiology into a structured, teachable, and measurable approach to cold and heat exposure.
It is not a single protocol or a single product. It is a complete system — encompassing the science, the practice, the education, and increasingly, the technology that supports its application in both individual and commercial settings.
At its core, the Thermalist® Method is built on a simple but profound premise: your body is not designed to remain in thermal comfort. Deliberate exposure to cold and heat — structured according to the science of the Søberg Principle — activates biological pathways that strengthen the body at a cellular level, producing benefits that extend across metabolism, cardiovascular health, nervous system function, immunity, mental health, and longevity.
The Science Behind Cold and Heat — What Actually Happens in the Body
Understanding why the Thermalist® Method works requires understanding the physiology of thermal stress.
Cold water immersion triggers a cascade of measurable physiological responses:
• Brown adipose tissue (brown fat) activation — metabolically active fat that burns calories to generate heat, with significant implications for metabolic health and insulin sensitivity
• Norepinephrine release — studies show cold water immersion can produce a 200-300% increase in norepinephrine, with significant effects on mood, focus, stress resilience, and pain management
• Cardiovascular training — the vascular response to cold exposure trains the cardiovascular system's ability to regulate blood flow and manage thermal stress
• Immune system activation — regular cold exposure is associated with measurable improvements in immune function and inflammatory markers
Heat exposure — particularly structured sauna therapy — produces its own distinct set of physiological responses:
• Heat shock protein activation — HSPs play a critical role in cellular repair, protein folding, and protection against cellular damage and aging
• Cardiovascular conditioning — sauna exposure produces cardiovascular effects comparable in some measures to moderate aerobic exercise
• Growth hormone release — heat stress stimulates growth hormone, which supports muscle maintenance, fat metabolism, and tissue repair
• Longevity associations — epidemiological studies have linked regular sauna use to significantly reduced all-cause mortality and lower rates of cardiovascular disease
The deliberate alternation of these two states — structured according to the Søberg Principle — produces a combined effect greater than either cold or heat alone. It creates a comprehensive training stimulus for the body's regulatory systems simultaneously.
The Thermalist® Method does not ask you to endure discomfort for its own sake. It asks you to use thermal stress intelligently — because the physiology is unambiguous about what structured cold and heat exposure does to the human body.
From Research to a Global System
What began as a research question in a Copenhagen laboratory has evolved into something much larger.
Over the past several years, the Thermalist® Method has grown from a scientific finding into a global system — one that is now being practiced, taught, and implemented in real-world settings across more than 25 countries.
More than 250 instructors have been trained and certified in the Thermalist® Method. The method has been implemented in premium wellness facilities, luxury spa hotels, fitness clubs, and health clinics across Europe, North America, Asia, and Australia.
The Søberg Principle has been adopted as the scientific foundation for contrast therapy programming by practitioners worldwide — not because it is a wellness trend, but because it is peer-reviewed science that produces measurable, reproducible results.
And the system continues to develop. The Thermalist® Recovery System — now available for licensing to selected wellness and hospitality operators at thermalist.com — represents the next evolution of the method: a complete operating system for structured contrast therapy in commercial wellness settings, incorporating programming, staff certification, guided experiences, and a member-facing technology ecosystem.
The Thermalist® Method for Individuals — Four Online Courses
For individuals who want to learn the Thermalist® Method and apply it in their own lives, Dr. Søberg offers four online courses at the Søberg Institute — each designed for a different stage of the journey.
Thermalist® Method at Home
A 3.5-hour self-paced online course introducing the full Thermalist® Method — the science, the Søberg Principle, sauna therapy, cold water immersion, and breathwork — distilled from over a decade of research into practical, accessible lessons. The ideal starting point for anyone new to the method.
Available at soeberginstitute.com
Cold Water Immersion Course — by Dr. Susanna Søberg, PhD
An evidence-based course covering the complete science of cold water immersion — including brown fat activation, cold shock response, hypothermia, cardiovascular safety, Raynaud's syndrome, and practical guidance for beginning a safe and effective cold water practice. Rated 5 stars by more than 400 students worldwide.
Available at soeberginstitute.com
The 3 Week Thermalist Cure®
A structured three-week programme that integrates cold exposure, heat therapy, and breathwork into a single daily practice — with content released each day throughout the three weeks. Rated 5 stars by more than 300 students. The most comprehensive individual introduction to the full Thermalist® Method.
Available at soeberginstitute.com
The Søberg® 12-Week Reset
Dr. Søberg's most comprehensive individual programme — a guided 12-week journey through cold exposure, heat therapy, breathwork, sleep, movement, and nervous system regulation, designed to help participants build their own personal metabolic protocol. Over 8 hours of premium video content released over 12 weeks.
Available at soeberginstitute.com
The Thermalist® Recovery System — For Wellness Operators
The Thermalist® Method is not only for individuals. For wellness operators — premium spa hotels, fitness clubs, recovery facilities, and hospitality groups — the Thermalist® Recovery System offers the complete science-backed contrast therapy operating system as a licensable programme.
The Recovery System translates the peer-reviewed science of the Søberg Principle and the Thermalist® Method into a structured commercial offering — with contrast therapy programmes, staff certification, guided sound experiences, and a member-facing app ecosystem built on published science.
The system is now launching to selected founding partners. Operators interested in bringing structured, measurable, science-backed contrast therapy programming to their facilities are invited to apply at thermalist.com.
The Thermalist® Recovery System is available for licensing to selected premium wellness and hospitality operators. Visit thermalist.com to learn more and apply for partnership.
Why the Thermalist® Method Is Different
The wellness industry is full of methods, protocols, and programmes that claim to be science-backed. Very few of them are built on published, peer-reviewed research by the scientist who conducts it.
The Thermalist® Method is different for one fundamental reason: it was built from the science up — not from the market down.
The Søberg Principle was published in Cell Reports Medicine before the Thermalist® Method became a global system. The research came first. The practical application followed. The system is the translation of that research into the real world — not a brand that commissioned research to support its marketing.
That distinction matters. It is the reason the method is trusted by practitioners across 25+ countries. It is the reason it has been discussed on Huberman Lab, The Joe Rogan Experience, and in The New York Times. And it is the reason the Thermalist® Recovery System is positioned as a credible, evidence-based operating system for premium wellness operators — not another trend-driven wellness concept.
About Dr. Susanna Søberg
Dr. Susanna Søberg is a Danish metabolic scientist with a PhD from the University of Copenhagen, the founder of the Søberg Institute and Thermalist®, and the author of the international bestseller Winter Swimming.
Her research has been published in Cell Reports Medicine, discussed on Huberman Lab and The Joe Rogan Experience, featured in The New York Times, The Times, The Guardian, and BBC Radio, and applied in wellness settings across more than 25 countries.
She is available for keynote speaking, scientific advisory roles, brand partnerships, and newsletter sponsorships. Enquiries via soeberginstitute.com/pages/partner-with-dr-soeberg.
To explore her online courses, visit soeberginstitute.com. To learn about the Thermalist® Recovery System for wellness operators, visit thermalist.com.
Learn more about Thermalist Education