- What is brown fat?
Brown fat is a fundamental tissue in mammals that, at the time, was mostly understood as something that rodents used to help heat themselves during hibernation. The spongy, fatty tissue looks a lot like ordinary white fat that most mammals use to store excess caloric energy. But where white fat can serve as an insulator, brown fat has an active role to burn white fat to generate body heat. It’s the only mammalian tissue whose sole purpose is to make heat, or, in scientific terms, thermogenesis. In humans, however, BAT was only considered important in newborns. The very first challenge that a human faces once it is born is the constant fight to keep a stable body temperature. With a relatively high ratio of surface area to body mass, babies lose heat much faster than adults. This is why many premature babies spend their first weeks in incubators. The easiest way for an adult to rapidly increase their core temperature is through shivering. The activity of muscles generates a moderate amount of heat as a byproduct of movement. Fresh from the womb, infants lack significant musculature and can’t shiver themselves warm. Instead they are usually born with a layer of chubby rolls of insulating white fat. When their core temperature begins to drop, BAT turns on, sucks white fat from their system, and releases a cascade of heat energy. Once the infant becomes a child and its muscles begin to tone up, the white baby fat disappears and along with it the brown adipose tissue. By the time they’re adults, most humans have very little BAT in their system. What does remain is often just a few teaspoons’ worth of the tissue along their spine and shoulders. Most doctors figured that BAT was simply irrelevant for adults. In fact, most adults have so little BAT that anatomists didn’t even know it existed
And thus, BAT might not only help explain the mysteries of how Neanderthals survived through ice age winters, but also how modern humans could use it to get through their own winters as well. Oncologists now note that PET/CT scans taken in the winter months have more instances of BAT than in the summer, suggesting that it comes and goes with the seasons.
- What is wedge?
It’s the same wedge that a person uses to calm their nerves when standing in the snow, withstand shivering, hold their breath just a little bit longer, stop feeling ticklish, or hold back the flow of urine as they search for a bathroom. It seems like a small thing, but it’s a window into the root of a human power, and a place that, if exercised, can help unlock the body’s hidden biology. Freedivers who descend hundreds of feet below the surface of the ocean on a single breath sometimes call it the “master switch”: It’s the point where the body meets the mind. Any preprogrammed physical response is potentially susceptible to the wedge as long as it has three key characteristics. First there needs to be a clearly identifiable external stimulus. Second, that stimulus must trigger a predictable automatic biological response or reflex. Third, that physical response must elicit a feeling or sensation you can visualize or imagine independently of the external trigger. If the reflex has these characteristics, then using the wedge is as simple as setting up an environmental stimulus and then resisting the sensation that it triggers. Over time it becomes easier to maintain the tension between reflex and mental control. That said, not every reflex is an ideal candidate for training. Allergic responses might make for interesting test cases, but like many autonomic functions, they exist for a reason. Sneezing removes allergens from the body and is part of a preset program that has enabled species to survive until today. Suppressing allergic reflexes could lead to all sorts of physical complications. The same goes for learning to hold your bladder at bay indefinitely. Sure it’s possible, but it is not generally a good idea.
Of course, this is a pretty well-understood body hack. When you clear your lungs of CO2 and fill them with air, there’s enough stored oxygen to do a fair amount of physical exertion. However, your brain doesn’t intrinsically know how you’ve changed the oxygen baseline to perform a little bit better. Every time you do this you effectively grow a slightly stronger wedge.
Both of these exercises work to find the meeting point between the body and the mind. Your brain has a subconscious map of what it thinks are its personal limits based on previous experiences. That map isn’t particularly well-drawn for anyone who isn’t already the sort of athlete who constantly pushes themselves to the edge of their physical abilities.
- How does body respond to holding breath?
The urge to gasp for air is not directly linked to the amount of oxygen in the bloodstream. That’s because, for some reason that has been lost in the convoluted process of evolution, the body cannot sense oxygen, only its byproduct. Breathing is a two-part process—inhaling to bring oxygen to the lungs and exhaling to expel carbon dioxide (CO2). When the brain senses too much CO2 in the bloodstream, the chest tightens, vision blurs, and just about every muscle from the abdomen to the forehead clenches down hard. When we talk about this sensation we usually say that we need to take a breath. However, on a physiological level your body wants to expel CO2. It sounds counterintuitive but it’s easy enough to test. Take a deep breath in and hold it until you feel the urge to breathe. Then release a little bit of air. With less CO2 in your lungs you will feel like you can hold your breath a little bit longer. That’s because you’ve removed a potentially poisonous waste product from your body and your nervous system has turned off the alarm bells. This basic gas exchange creates an opportunity to trick your nervous system into extending the amount of time that you can hold your breath, thus leading to the very first training technique to crack into your nervous system.
- Why mediation?
There’s a mental routine that you can do alongside the breathing. One of the goals of this practice is to shut down the higher cognitive functions so that you can communicate directly with your lower brain functions. The brain burns far more energy than any other part of the body. In a typical day an adult male burns 2,200 calories, but the brain gobbles up 15 to 20 percent of that energy.
- Why should you get cold without shivering?
If your body can’t shiver itself warm again or rely on the insulating properties of your white fat, its only remaining option is to start ramping up your metabolism. This is to say, you will begin passively generating brown fat and building up your stores of mitochondria if you can suppress your shiver response.