Most of What You Have Been Told About Cold Plunging Is Wrong
Three claims I hear every week, the one that survives, and the number the science actually supports
Dr. Susanna Søberg, PhD · soeberginstitute.com
I am a metabolic scientist, and most of what I see said about cold plunging online is wrong.
Not out of malice. The practice moved faster than the research reached the public, so the loudest advice filled the gap. It usually repeats three claims. Colder is always better. Longer is always better. And it burns meaningful fat.
I have spent my research career studying how the body responds to cold and heat, and I published the protocol behind much of this conversation, the Søberg Principle, in the journal Cell Reports Medicine. So let me take the three claims seriously, tell you which one survives, and then give you the actual number the science supports, so you leave this with something you can use tonight.
Claim one: colder is always better
This is the one I would most like to retire.
The belief is that a colder plunge is a better plunge, so the goal becomes chasing a lower number every time. That is not how the benefit works.
Cold is a stress. A controlled, useful stress, but a stress. The adaptation does not come from the severity of the shock. It comes from your body learning to respond to it and then recover. Past a certain point, colder water does not give you more of that. It gives you a larger stress that takes longer to come back from, and for some people it tips into a dose their nervous system spends the rest of the day paying off.
Meaningful adaptation begins at temperatures far more moderate than most plunge culture admits. The number on the thermometer is not the prize. Your recovery is.
Claim two: longer is always better
Same logic, same error.
If a short exposure is good, a longer one must be better, so people hold on, count the minutes, and treat endurance as the achievement. But the useful signal from cold arrives early. Extending the exposure well past that point does not multiply the benefit. It multiplies the recovery cost, and it raises the risk, because the longer you stay in genuinely cold water, the more your core temperature actually falls.
This is where the culture gets it backward. The person shivering through ten minutes is not getting ten times the adaptation of the person who did one. They are getting a bigger bill.
Short, consistent, and repeated beats long and heroic. The body adapts to the pattern, not to the single hard effort.
Claim three: it burns meaningful fat
This is the one that gets oversold the hardest, so I want to be precise.
Part of it is true. Cold does activate brown fat, the metabolically active tissue that generates heat, and it does raise your energy expenditure while you are cold. That mechanism is real and it applies to everyone.
But the leap from there to “cold plunging is a weight loss tool” does not hold. The extra energy you burn during a short cold exposure is small in the context of a whole day of eating and moving. If someone is selling cold to you mainly as a way to lose fat, they have crossed from the proven pile into the oversold one.
The real metabolic value of cold is not the calories burned in the moment. It is what regular exposure does over time, training your metabolism to be more flexible and more responsive. That is the benefit worth practicing for. The fat loss promise is the part that sets people up to be disappointed.
So which claim survives?
None of the three as stated. But underneath all of them is one thing that is genuinely well supported by the science, and it is the reason I built my work around cold in the first place.
Regular, moderate cold exposure produces real adaptation. It shifts your nervous system, supports metabolic flexibility, and trains your body to move between stress and recovery more efficiently. That is the proven core.
Notice what it is not. It is not colder, not longer, not a shortcut to fat loss. It is moderate, consistent, and repeated.
The number no one gives you
Here is the part most cold content leaves out, because a real number is harder to sell than a bold promise.
In my research, published in Cell Reports Medicine, the pattern that came with the metabolic benefit worked out to roughly eleven minutes of cold and about fifty-seven minutes of heat per week, spread across a few sessions. Not per day. Per week.
Read that again, because it is far less than the internet implies. You do not need to suffer daily. You do not need to chase a colder number or a longer hold. A short cold exposure a few times a week, ideally paired with heat, is enough to drive the adaptation that matters.
That is the honest headline. Eleven minutes of cold a week, done consistently, beats a punishing plunge you dread and abandon. The starting line is simpler and gentler than the culture around it, and it is yours now.
Why the myths matter
When the loudest advice is colder, longer, and you will lose weight, two things happen. People who follow it push too hard, recover poorly, and sometimes get hurt. And people who try it, get none of the promised weight loss, and conclude the whole practice was a scam.
Both are a loss, because the proven part is genuinely good for you. It just does not look like the version being sold.
This is the whole reason I write. Not to defend cold, and not to attack it, but to show you where the line between evidence and hype actually sits, so you can practice the part that works and ignore the part that does not.
If this helped
The free pieces here give you the honest science and a safe place to start. The paid pieces go deeper into the actual practice: how to build up to the weekly amount safely, how to adjust it for your own body, your cycle, and your goals, and how to know when you are doing too much. If you want that depth, you can upgrade below. If you only want the honest science, staying free is completely welcome, and you will always get pieces like this one.
Either way, subscribe so the next one reaches you. This is part of a series where I take the biggest claims in cold and heat, one at a time, and separate what is proven from what is sold.
And tell me in the comments: which claim have you heard the most? I am building the next pieces around the ones you bring me.
Dr. Susanna Søberg
Reference: Søberg S, et al. Cell Reports Medicine, 2021.