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Brown Fat and Winter Workouts – The Apeiron Life Perspective



What is it:

When the outdoor temperatures dip, it’s normal to feel the gravitational pull of the couch rather than the trails. But exercising in the cold weather has vast mental and physical benefits as long as you’re adequately dressed. What happens in your body when you’re working out in the cold is rather interesting.


Human bodies like to be in homeostasis, a steady self-regulating state optimal for survival. Our ideal core body temperature is around 37 degrees Celsius or 98.6 degrees Fahrenheit. To keep our body’s various systems running smoothly, the body favors staying at this temperature. If we overheat, we sweat. If we’re cold, we shiver. Even though exposing yourself to cold temperatures feels unpleasant, an array of hidden health benefits await.



Purported claims:

  • Burn energy more effectively

  • Turn inactive white fat into metabolically active brown fat

  • Enable better athletic performance

  • Boost your mood and reduce anxiety



What the science says:

When we exercise in moderate or hot temperatures, we sweat to cool ourselves off, but this doesn’t dissipate energy. In cold environments, however, we burn more calories even at rest because our bodies have to use more energy to heat our bodies to keep the ideal core temperature. So, if you want to lose weight and burn more energy, exercising in cold weather makes sense. Our muscles shiver to produce heat for the first 10-30 minutes of cold exposure. However, shivering causes lactic acid to build up in the body, so after a while, the body turns white fat (the kind that stores excess energy) into calorie-burning beige or brown fat. This process is called non-shivering thermogenesis. You might have experienced this if you’ve been exposed to cold for a while. For example, you stayed in your backyard patio entertaining guests shivering in the late fall evening without a sweater. And when you finally go indoors, you suddenly feel exhausted, as if you’ve done an exhaustive workout even though you didn’t.


Brown adipose tissue (BAT) is essential for metabolic health. BAT clears 75% and 50% of the total glucose and triglycerides from the circulation, respectively. Some studies have also reported significantly lower blood HbA1c, total cholesterol, and LDL cholesterol levels in the BAT-positive group than in the BAT-negative group. The more brown fat you have, the more it decreases the risk of developing insulin resistance or diabetes and increases your cardiometabolic health.


Some studies have also examined the timing of cold exposure and whether it affects brown fat activation. Interestingly, a study from the Netherlands showed that early morning cold exposure seems to be more effective in activating brown fat, but only in men. According to researchers, the reason might lie in the sex hormones and the slightly different circadian rhythms between the two sexes. In addition, circulating free fatty acid concentrations, triglycerides, and cholesterol levels were higher in women after cold exposure in the morning than in the evening. The study, which was conducted in the Netherlands, was small, and the authors noted that additional, more rigorous research is needed before we can draw definite conclusions on timing and cold exposure.


When exercising, your body works hard to keep the core temperature from rising too much. When you work out in hot or humid conditions, a lot of energy goes into this cooling process, and your performance suffers. On the contrary, when you exercise in cool or even cold temperatures, as long as you’re adequately dressed, your body can devote all its resources to your performance. This is evident when you look at world records in the marathon or any endurance event. They have almost always been done in ideal, cool temperatures. So, as an athlete, embrace the cooler temperatures and work on your endurance. It can improve your cardiovascular fitness and performance at race time.


There is also an interesting connection between cold weather exercise and mood. Finland could be called “the capital of ice swimming” (swimming in the frozen lake or sea), and there have been several studies showing that people who regularly engage in ice swimming have improved energy levels, general well-being, decreased tension, anxiety, and fatigue compared to people who don’t take part in this routine. One of the studies also reported that the swim group had reduced pain from rheumatism, fibromyalgia, and asthma compared to the controls.


The hypothesis behind these findings is that cold exposure produces a shock to the system, initiating a fight-or-flight response in the body. The sympathetic nervous system is fully awake: the pituitary gland stimulates the circulation of feel-good hormones such as endorphins and dopamine that lift your mood and energy levels. At the same time, the adrenal gland secretes stress hormones such as adrenaline, noradrenaline, and cortisol that increase your pain tolerance and suppress inflammation. People who regularly participate in ice swimming often describe their feelings afterward as ‘euphoria,’ a feeling of intense happiness and calm. But you don’t have to go to that extreme to get the mood-boosting benefits of cold exposure. A similar study in the U.K., where participants engaged in open-water swimming (temperatures varied between 60-70 degrees Fahrenheit) for 10 weeks, registered increased positive mood and well-being compared to the control group.


Brown fat and its effect on metabolism has been challenging to study as humans have very little of it after childhood. But since obesity has become a worldwide epidemic, brown fat and its potential in fighting it has risen in recent years. There seems to be some disagreement among researchers about the ideal temperature for fat browning to start and how long one should expose oneself to this temperature. But the leading theory is that mild temperatures, around 60-64F, which is cold enough for the body temperature without causing too much shivering for a couple of hours, are best for fat browning to kick in.



Our take:

People in the United States are used to being in perfectly regulated, comfortable environments, whether at home, office, or in the gym. We crank up the furnace in the winter and turn on the AC when the outdoor temperature exceeds 75 Fahrenheit. But being a little bit chilly, at least occasionally, is probably healthier for you in the metabolical sense.

Dark winter months are often hard for our mental well-being, and with the holidays bringing additional stress and often unhealthy amounts of eating and drinking, escaping outdoors for a brisk walk, jog, or even a swim in an outdoor pool could do wonders for our overall health.



Will this benefit you?

If you’re interested in your metabolic health, and we all should be, then finding ways to turn unhealthy white fat into brown fat could be a game changer. It is also probably not too far-fetched to say that most of us could benefit from a healthy routine that might decrease our stress while increasing our bliss. Most of us are engulfed by the digital world daily and rarely have to step into an uncomfortable outside environment. Challenging our physical and mental comfort zone by being cold and resisting the urge to stave off the elements could yield surprising benefits to our overall well-being and resilience.



Still curious to try it? Here is what to keep an eye on

Cold weather exercise does have some risks involved. Blood flows from the extremities to the working muscles and vital organs during exercise. Protecting hands, feet, and the head is critical. If you’re exercising in freezing temperatures, you should also dress reasonably to stave off the risk of hypothermia, a dangerously low body temperature when your body loses heat faster than it can produce it.


Cool conditions will result in shrinking blood vessels, which can heighten blood pressure and cause adverse cardiovascular events, so if you have cardiovascular disease, you should talk to your physician to see if working out in the cold weather is okay for you. And even though you’re not sweating like you would on a warm day, drinking enough fluids is still required. Lastly, colder conditions mean a greater risk of injury or muscle strains, so your warm-up routine should last a bit longer than usual.



References and additional reading:

Exercise in the cold to active the brown fat tissue: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6466122/

BAT and triglyceride clearance: https://pubmed.ncbi.nlm.nih.gov/21258337/

BAT and insulin resistance and diabetes risk: https://www.jci.org/articles/view/78362#B104

Sex differences in BAT activity: https://pubmed.ncbi.nlm.nih.gov/34126190/

Cold-water swimming and energy levels and mood: https://www.tandfonline.com/doi/pdf/10.3402/ijch.v63i2.17700

Supercharging brown fat to battle obesity:



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