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How Cold Plunging May Boost Metabolism

What if there was another tool to help combat obesity, heart disease, stroke, type 2 diabetes, and other life-threatening diseases? What if we ditched the toxic diet culture and returned to our roots to help boost metabolism, reduce cardiovascular risks, and improve our quality of life?

The skinny on brown fat

Researchers are now interested in a little-known organ called brown adipose tissue (BAT) or brown fat, a type of fat that regulates body temperature. Brown fat activation may become another tool (along with exercise, incorporating whole foods into our diets, and other healthy habits) to increase metabolic and cardiovascular health.

Foremost researcher of cold water’s effects on metabolism, Susanna Søberg, wrote a book called Winter Swimming that lays out all her research on brown fat.

According to her, brown fat was originally thought to appear only in newborns as a mechanism to keep them warm, since shivering is not developed in infants. But in the 1970s, brown fat was discovered during PET/CT scanning of adults. So the question arose, why does brown fat stay with us as we age? It must have some important functions or evolution would have caused us to lose it over time.

White fat vs. brown fat

White fat is the stuff we need a little of to survive, but not too much — otherwise it can pose health risks. White fat cells each contain a large droplet of lipid or fat (triglyceride), and a small amount of mitochondria (the cell’s energy powerhouse and metabolism engine). The lipid droplet pushes the mitochondria to the cell’s outer edges, which makes it difficult for the mitochondria to create energy. Fat burn is slow.

Brown fat is the healthy, thermogenic fat that works hard for us constantly when we’re eating, sleeping, exercising, and getting cold! It is a temperature-balancing organ that lives close to the central nervous system and can be found in up to six spots in the body. Each cell of brown fat contains multiple small lipid droplets instead of one big one. The cells also contain more mitochondria – which give brown fat its brown color – that are spread out to produce energy quickly.

How does brown fat work?

Brown fat’s main job is to keep us warm by burning energy. We can call it a radiator and the brain a thermostat. It follows this process: nerves in the skin detect cold temperature and send the signal to the brain. Adrenal glands release norepinephrine which activates brown fat cells to perform thermogenesis, or heat production. Thermogenesis happens within the brown fat cells’ mitochondria.

To break it down further, mitochondria split the fat inside the cell by producing adenosine triphosphate (ATP) - a molecule that carries energy within the cells – and the energy is released directly as heat in the body. The brown fat cells pull fat and sugar from the bloodstream as fuel to create energy.

When the skin detects cold temperatures, immediately brown fat begins burning energy to keep you warm. (You get metabolic benefits within a very short time of being in the cold!) When that is no longer enough, your muscles contract and you begin to shiver. If you find yourself shivering after a very short period of time, chances are your brown fat isn’t developed or you’ve lost some of it.

Why does brown fat matter?

  1. As mentioned above, brown fat pulls glucose and lipids (sugar and fat) from the bloodstream and burns it as energy. As a result, sugar and fat are reduced in the bloodstream, which can benefit the metabolism, cardiovascular system, and even treat cardiovascular disease.

  2. Less brown fat usually equals higher blood pressure and cholesterol.

  3. Development and activation of brown fat may also be able to ward off atherosclerosis — a build-up of fat, cholesterol, calcium, and other substances in the blood in the form of plaque. Atherosclerosis has the potential to cause inflammation and blood clotting, so it’s not something we want!

Do I have brown fat?

Typically, women have more brown fat than men. Many of us may currently have lower levels of brown fat since we live in a modern world where comfort is prioritized. We may not have to face freezing cold or burning hot temperatures the majority of the day — we can go indoors and crank the AC or heater to achieve comfort.

People living in different parts of the world with different climates will have varying levels of brown fat. For example, if you or your ancestors grew up in a very hot climate and didn’t need brown fat to keep warm, you may have a lower baseline level of brown fat. But through deliberate cold exposure, that can change.

How can I activate or develop brown fat?

Søberg discovered that habituated winter swimmers were able to protect their core temperature just as well as unhabituated swimmers, but they shivered much less. She hypothesizes that swimmers who are used to the cold have increased their thermogenesis and metabolism through regular cold exposure.

Søberg’s studies of winter swimmers and brown fat suggest that we, too, can acclimate our bodies to the cold. As we deliberately expose our bodies to the cold, our brown fat will increase and keep us warm for longer.

Here are some safe ways to activate your brown fat, boost your metabolism, and train your body to stay warm in the cold:

  • Cold plunge or cold shower regularly— you only have to submerge yourself up to the neck in a plunge, and only spend 30-90 seconds in the water for brown fat benefits to kick in!

  • Implement the Söberg Principle — if you’re doing a cold plunge and sauna, start with the cold and end with the cold. That way, you force your brown fat to heat your body up from the inside.

  • Sleep in a cold room — it’s good for your rest, and it will also increase your insulin sensitivity!

  • Turn the temperature down in your house — you don’t have to live in an icebox, just a few degrees colder than you’re used to.


Brown fat is like a muscle. If we don’t use it, we lose it! Let’s face it though, it can be intimidating to jump into a bucket of icy water or turn our cozy warm shower to cold. But research shows you don't have to be in the cold water for that long to reap benefits. And just like starting a new exercise regimen or developing a new productive habit, you only have to start small and it will get easier. With consistency, you’ll strengthen your metabolism and mental resolve, and pretty soon you’ll #cravethecold.


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