The Proof with Simon Hill Science of ice baths, brown fat and metabolism | Susanna Soeberg, PhD
What happens to your body when you plunge into icy water or unwind in a sauna? A researcher explores brown fat, metabolism, winter-swimming culture, and the science behind popular cold-and-heat claims. They also discuss beginner safety, how men and women may respond differently, and why the first dip can feel like a battle with your own nervous system.
02:52:46
Sauna Frequency and Heart Health
- Sauna use 2-3 times per week reduces cardiovascular risk and mortality by over 25%.
- More sauna sessions increase benefits but exceeding daily use may strain the heart.
Cold Exposure Raises Metabolism
- Cold exposure increases metabolism by activating brown fat mitochondria and burning glucose and fat.
- Higher metabolism supports health but weight loss effects remain unclear and depend on diet.
Shivering vs Brown Fat Heat
- People with less brown fat shiver more to generate heat as a compensatory mechanism.
- Adapted cold swimmers delay shivering due to efficient brown fat thermogenesis.
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Introduction
00:00 • 2min
How Cold and Hot Exposure Affects Human Health
01:55 • 2min
What's the Follow-Up to Winter Swimming?
03:30 • 2min
Is There an Appetite for Winter Swimming?
05:48 • 3min
The Winter Swimming Culture in Denmark?
08:25 • 2min
The Effect of Winter Swimming on Physiology
10:24 • 5min
How to Sleep in a Very Cold Room
15:20 • 3min
Is There a Pin in Brown Fat?
17:51 • 2min
Is There a Good Reason Not to Do This?
20:20 • 2min
The Culture of Winter Swimming
22:07 • 2min
Do You Have a Fear of Going Down in the Dark Water?
24:25 • 2min
Cold Water Immersion and Sauna Heat Exposure
26:36 • 3min
Cold Water Immersion Could Be the Future of Preventive Medicine
29:30 • 2min
Do You Have a Hermetic Stress Protocol?
31:53 • 2min
Is There a Growing Trend to Deliberate Cold Exposure?
34:21 • 4min
Cold Water Immersion and Unregulated High Blood Pressure
38:42 • 2min
What's Happening in the Cold Water?
40:28 • 2min
Activation of the Sympathetic Nervous System
42:07 • 2min
How Does the Cold Water Change the Physiology of the Body?
43:41 • 3min
How Do You Get Afadapted to Cold Water?
47:07 • 2min
The Brown Fat Cell Is Very Different From White Fat
48:48 • 3min
Is There a Test That Can Quantify How Much Brown Fat I Have?
52:02 • 4min
Can You Transform Your Brown Fat?
56:24 • 2min
How Can We Grow More Brown Fat?
58:22 • 2min
The Benefits of Activating the Brown Fat in the Cold
59:55 • 4min
Type 2 Diabetes - Is There a Cohort Study?
01:04:06 • 2min
Sauna Betters and Cardiovascular Diseases
01:06:25 • 3min
Do You Know How Many Minutes Per Session Is Best?
01:08:55 • 2min
How Much Sauna Do You Need to Do a Week?
01:10:55 • 2min
Heat Stress and Cold Stress Are Acting Differently
01:13:14 • 3min
How Does Cold Water Increase Your Metabolism?
01:15:57 • 3min
How Much Do You Burn From One Minute, Two Minutes, Three Minutes?
01:18:35 • 2min
How to Increase Non-Shivering Thermogenesis
01:20:33 • 3min
How to Get the Most Out of Your Winter Swimming
01:23:16 • 2min
How to Reduce the After Drop in Your Core Temperature
01:25:16 • 2min
Do You Have to Change the Temperature to Keep Your Cells Younger?
01:27:44 • 5min
Train Your Temperature Sensitivities and Keep Your Brown Fat Alive
01:32:19 • 2min
Increasing the Efficiency of Your Brown Fat
01:34:18 • 4min
Women Have More Brown Fat Than Men
01:38:03 • 4min
Is It 22 Degrees Celsius in Room?
01:42:23 • 2min
How Does Deliberate Cold Exposure Affect Your Immune System?
01:44:17 • 6min
The Importance of Cold Showers in Training and Bodybuilding
01:50:10 • 3min
Is Ice Exposure Good for Hypertrophy?
01:53:33 • 3min
The Cold Shower Before Bed
01:57:01 • 2min
Dopamine and No Adrenaline Increase in the Cold Water and It Helps Your Mental Balance
01:59:01 • 4min
Dopamine and Oxytocin Increases in the Cold Water
02:03:02 • 2min
Dopamine Noradrenaline Oxytocin Is Increased in Cold Water?
02:05:09 • 3min
Can Cold Water Swimming Really Cure Depression or Anxiety?
02:07:42 • 2min
Cold Water Therapy for Alzheimer's Disease
02:09:15 • 5min
How to Control Your Nervous System the First Time
02:14:14 • 3min
The Cold Water Is Not a Competition
02:17:32 • 2min
Is It Important That You Work Your Way Up to 11 Minutes Per Week?
02:19:19 • 3min
How Much Do You Do?
02:22:14 • 4min
Do You Have a Swimsuit On?
02:25:53 • 3min
The Disappearing Penis
02:28:28 • 2min
Change the Temperature Over Time
02:30:22 • 2min
Is There a Difference Between Men and Women on Winter Swimming?
02:32:20 • 3min
Sauna
02:35:43 • 2min
Is There a Myth About Head Dunking in an Ice Plunge?
02:37:33 • 6min
Baptism by Fire Is Your First Dip in the Cold Water
02:43:20 • 2min
Eyes at Eye Level
02:45:24 • 2min
I'd Love to Be a Viking So Tell Me About Reaching Viking Status
02:47:16 • 2min
Thermolist - Book Release in Danish
02:49:43 • 2min
Episode #250. Ice baths and other forms of cold water exposure have gained a huge amount of traction in the past few years. I’m joined by expert Dr Susanna Søberg to examine what the science says – is cold water exposure safe? What does the research say about the bold health claims? Is brown fat just a buzzword? How do you safely and effectively implement hot and cold exposure into your life? Dr Søberg answers these questions and many more in this three-hour deep dive into cold water immersion.
Specifically, we discuss:
- Intro (00:00)
- The tradition of winter swimming (01:52)
- Cold water swimming and activating brown fat (09:44)
- Dr. Søburg's personal experience with cold water bathing (23:13)
- Funding hurdles and potential benefits of cold water immersion (25:34)
- Cold water immersion and the body's response (33:36)
- Brown fat activation and more physiological responses (40:45)
- What is brown fat? (45:54)
- Is brown fat genetic? (55:28)
- Benefits of activating brown fat (58:32)
- Winter swimming, sauna, and disease: what the data says (1:01:10)
- Metabolism and shivering (1:13:01)
- Brown fat activation and muscle building (1:25:06)
- Who has more brown fat: Women or Men? (1:36:33)
- Chronic inflammation, exercise, and more benefits of deliberate cold exposure (1:46:11)
- Cold water immersion for beginners (2:06:18)
- The minimum threshold for health benefits using cold and heat (2:15:03)
- Clothes or no clothes? (2:22:57)
- Temperature regulation and gender differences (2:26:30)
- Safety protocols & understanding ice plunging lingo (2:34:08)
- Outro (2:47:18)
To connect with Dr Susanna Søberg, you can find her on Instagram, Twitter, Facebook, TikTok, and LinkedIn. Head to her website, www.soeberginstitute.com, to learn more about Dr Søberg’s work – including her research and her book Winter Swimming. Friends of The Proof can also receive a 10% discount on her Thermalist course with code SIMONHILL.
Discover more insights and supporting resources in the full show notes.
Enjoy, friends.
Simon
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Simon Hill, MSc, BSc (Hons)
Creator of theproof.com and host of The Proof with Simon Hill
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