Do you want to speed up your metabolism and burn more fat? activate your brown fat ⋆

‘At some point along the way, we seem to have confused comfort with happiness.’ – Dean Karnazes

‘No man is more unhappy than he who has not suffered adversity, because he dies without proving himself.’ – Seneca

Many of the inventions that contribute to what we call progress are actually more layers of isolation between us and nature. Often the goal of these extra layers is to make us feel more ‘comfortable’. There is nothing wrong with comfort per se, but when being comfortable is our life goal, we lose something valuable.

The problem with this continual pursuit of comfort is that the more we isolate ourselves from nature, the more we depend on external supports to perform activities that our body could do on its own, the more our health suffers.

As I have ever explained, we are children of ice. We spent much of our evolution in the last ice age, which began 110,000 years ago and ended only 10,000 years ago. Our body is not only well adapted to the cold, but expects it.

By ‘eliminating’ winter (with down, thermal clothing, central heating, heated car seats, chunky sole shoes…) We disconnect from one of the elements with which we evolve, the ‘heat stress’. And there is growing evidence that this plays a relevant role in the obesity epidemic of recent decades (studies).

It will always be a secondary factor if we compare it with food and physical exercise, the two fundamental pillars, but it is one more piece of the puzzle of our well-being.

Our body thrives on more variability, less routine. In exercise, in food, and also in temperature.

Before we get down to business, let’s explore some proven benefits of cold exposure:

  • Improves fat burning and glucose absorption by the musclesstudy), thanks in part to the greater activation of the adiponectin hormone in the face of cold exposure (study). Low levels of this hormone are linked to obesity, diabetes, and more cardiovascular disease (study).
  • Strengthens the immune system (study): While prolonged exposure to cold may weaken immune function, it seems clear that short and intense exposures strengthen it (study, study), while increasing the presence of certain antioxidants, such as glutathione (study).
  • Extends the longevity of cells, preventing the mTOR pathway and promoting autophagy (elimination of ‘metabolic waste’ from cells), similar to what is achieved with intermittent fasting. Many of the studies that exist are still in mice, but it is a promising line of research.
  • Decrease pain associated with different conditions, such as arthritis (study), through the stimulation of norepinephrine (study).
  • Improves symptoms of depression mild (study).

This is not to say that it is a bad idea to shelter from the elements, but we must also have short and intense exposures (Something like high intensity intervals of cold :)) .

In survival courses they teach you the rule of 3. Your life is in danger after 3 minutes without oxygen, 3 hours without shelter (at low temperatures), 3 days without water, 3 weeks without food.

That is, for your body, after getting oxygen, maintaining body temperature is the most important. You need those 36.5ºC (+/- 1ºC), and any small deviation represents an alarm. That is why it has mechanisms to maintain that thermal range at all costs, and the periodic activation of these mechanisms is beneficial. If they are never activated, they atrophy, and in recent years we have discovered an interesting relationship between exposure to cold and our metabolism.

It seems obvious to think that if you expose your body to cold, it must burn calories to maintain internal temperature. Nobody disputes that it is so. However, many ‘experts’ believe that it is not a sufficient amount to be significant. Spend 1 hour at zero degrees to burn 100 calories? The equivalent of an apple? I know the answer is «No thanks«.

But once we forget about the famous formula that blinds so many ‘experts’ (calories ingested less calories burned), the benefits of exposure to cold go far beyond the calories that are burned at the moment, and have much more to do with metabolic changes that are produced, specifically with the action of two elements:

  • Adiponectin, which as we saw before has an anabolic effect and favors fat burning.
  • Activation of the brown adipose tissue (or brown fat), which is today’s topic. I know when you hear about fat the question is usually ‘How do I remove it? ‘, but in this case you will ask ‘How can I have more?‘.

Brown fat

The brown fat, brown fat, or brown adipose tissue, is a very special type of fat, whose main mission is to produce heat, what it achieves through its numerous mitochondria and the activation of uncoupling protein-1 (UCP1).

The grace of this type of fat is that it can generate energy by skipping energy systems of our body, directly taking fat (white) and glucose to produce heat, without production of ATP, hence it is also known colloquially asfat burning fat‘.

When we are born, we have a significant amount of brown fat. It is logical, since babies are unable to shiver or move to escape the cold, and nature endowed them with this mechanism to maintain temperature.

For a long time it was thought that adults completely lost brown fat. Studies Recent show that this is not the case (mens, women). We retain a certain amount of this type of fat (more women), focused on the neck, upper back, and chest.

And the most interesting thing is that controlled exposures to cold not only activate this brown fat, but it is believed that it is possible to develop more (study). The amount of brown fat that an individual has plays a relevant role in the basal metabolic rate, that is, in the amount of calories used by the body at rest (study).

Some estimates (study) point out that only 50 grams of brown fat can represent up to 20% of the energy expenditure of an adult. Nothing bad.

Although the activation and development of new brown fat is achieved with exposure to cold, its effect goes much further, and recent studies indicate that brown fat dissipates a large part of the excess calories in the form of heat, preventing them from accumulating as normal fat. One of the effects that many people who perform cold therapy notice is that their body tends to generate more heat during the day, that is, increases metabolism.

On the other hand, multiple studies show an inverse correlation between the amount of brown fat and visceral fat and body mass index (study, study).

It seems that the fast (study) and exercise (study) can increase the activity of brown fat, and some interesting compounds such as bitter melon are being studied (detail), but their contribution to brown fat is far less than its main trigger: exposure to cold, formally known as cold-induced thermogenesis.

Having fun with the termogenesis induced by cold

The cold, like many of the stressors we generally talk about: intermittent fasting, exercise, exposure to bacteria… Generates a positive adaptation, through a concept called hormesis. This term originates from the world of toxicology, but applies to many biological processes. We could summarize it as the ability of an organism to become stronger when it is subjected to stress. Do you remember how your muscles grow? is another example of this same principle.

Enough theory. I imagine you already want to know how to start enjoying all the benefits associated with defying your fear of the cold. As always, you should start small. I list several alternatives, from the simplest to the most extreme. Advance at your own pace.

Less clothes, less heating

From time to time, go out with less clothing in winter. I am not saying that you spend hours in the snow in your underwear (remember the 3 hour rule without shelter), but a 20-30 minute walk in light clothing (rather than rolled under several layers of fabric) will facilitate a positive adaptation to the cold.

Train outdoors in winter. Several studies show greater fat loss in these conditions (study).

Lower the heat. Turn it off from time to time. It is not that you are shivering in the room, but a slight goosebump is healthy (also for your pocket).

Dive in, nothing

The conductivity of water is several times greater than that of air, so it is much more efficient when it comes to ‘extracting’ heat from your body, generating greater activation of brown fat.

You may have heard that Phelps consumes 12,000 calories. It is impossible to burn those calories for many hours that you swim a day (and from the photo it seems that you do not accumulate them as fat). Much of your caloric expenditure goes into maintaining your body temperature underwater.


The ideal is to swim in the sea or in a lake. If this is not possible, the pool is another option. Try that the water does not exceed 20-24ºC. Unfortunately, many heated pools are closer to 30 degrees.

Cold showers

In the morning, finish your normal shower with 2-3 minutes of cold water, focusing on the back and neck. Not only will it wake up your brain faster than a caffeine shot, but also your sleeping brown fat.

Remember also improve your testosterone levels.

As a preliminary phase for adaptation to the cold, some experts recommend immersing your face in ice water for 5 minutes a day. Don’t forget to take a break to breathe (rule of the 3 minutes without oxygen … :)).

Apply ice

Put an ice pack, for example rolled in a towel, behind your neck, while you read, study, watch television. 20-30 minutes is enough. I do not recommend it after training or for minor injuries.

You can also try an ‘ice vest’, but maybe it’s a bit excessive.

Ice baths

Some people rave about ice baths. I personally think there is a line between discomfort and pain It should be crossed only if you know what you are doing. Water less than 10ºC, or air less than 0º, can be dangerous for the uninitiated (the poison is in the dose).

If you dare, start by immersing yourself up to the waist in ice water (10-15ºC), 2-3 times a week for 10 minutes. When you get used to this, try diving up to your neck.

ice bath

What lovers of this technique affirm (I admit that I am not one of them), is that each time they can endure longer, or with colder water, without shivering. The explanation is that adaptation manages to activate brown fat longer, before moving on to the next line of defense, chills, when the body rapidly and repeatedly contracts muscles to generate heat.

If you want to experiment, go ahead, but start gradually. And maybe before you know it, you’ll be like Wim Hof ​​the Iceman.

Being comfortable being uncomfortable

As I said at the beginning, we are excessively afraid of discomfort, of leaving our (increasingly narrow) comfort zone. Our body thrives when it is subjected to adversity physical on a frequent (but not chronic) basis. The benefits go beyond the physical. Adversity also strengthens your mind. Only by leaving your comfort zone can you know yourself, and progress.

We must expose ourselves to the elements (in their proper measure), heat and the cold, instead of constantly depending on the thermostat in our rooms.

Do you want more information about the benefits of the cold? Read this article.