Third Pillar of Physical Fitness

We all know we should exercise and eat a balanced diet. But some argue we should also live more like early humans.

“The secret to cracking into our inner biology is as easy as leaving our comfort zones and seeking out just enough environmental stress to make us stronger,” writes journalist and anthropologist Scott Carney in his 2017 book, “What Doesn’t Kill Us: How Freezing Water, Extreme Altitude, and Environmental Conditioning Will Renew Our Lost Evolutionary Strength.”

Carney argues the basic idea behind “environmental conditioning” is that, for thousands of years, humans lived without the comforts of the modern world.

Today we still carry many of the same genes that helped us survive thousands of years ago.

“There’s an entire hidden physiology in our bodies that operates on evolutionary programming most of us make no attempt to unlock,” writes Carney.

Carney suggests environmental conditioning can help you reconfigure your cardiovascular system and combat autoimmune problems. And “it is a pretty darned good method for simply losing weight,” he writes.

Under the guidance of Wim Hof — a Dutchman who advocates a mix of environmental exposure and conscious breathing to gain control of our involuntary physical responses — Carney explores this world of ice baths and climbs shirtless up snow-covered mountain peaks.

For people who already push themselves hard — marathoners, triathletes, and Tough Mudders — the idea that being too comfortable could be bad for your health could strike a chord. There is some research to back up the idea that immersing yourself in the natural world could improve your health.

For example, a 2015 study found that 10 days of cold acclimation — spending up to 6 hours per day at 59°F (15°C) — boosted insulin sensitivity in eight men who were overweight and had type 2 diabetes. This change indicates a lessening of their disease symptoms.

  • Another 2015 study, showed that exposure to 63°F (17°C) for 2 hours per day for 6 weeks decreases body fat. This study included 51 healthy young male volunteers.
  • A 2014 study supports Hof’s method of using cold immersion and conscious breathing to suppress the innate immune response, possibly reducing excessive or persistent inflammation.

It’s worth noting all of the research cited above included a small number of subjects, which concerns some researchers.

“For human variation studies, you really want to have a great deal more than that. Working with just 24 people keeps you from making any sort of correlations,” Jessica Brinkworth, PhD, an assistant professor at the University of Illinois who studies the evolution of immune function, told Healthline.

She says what’s missing from research in this area is larger randomized studies that compare what happens to people undergoing environmental conditioning for many weeks with a similar group going about their normal routine.

She also says there need to be more studies that compare the benefits of environmental conditioning with other activities, such as aerobic or strength exercises, mindfulness meditation by itself, and a diet of whole foods.

Many parts of the body work together to form the immune system. Everything from the skin and bloodstream to the lymphatic system. The goal of the immune system is to prevent or limit infection. It does so by categorizing cells that are normal and healthy and those that may cause problems.

Under normal circumstances, our immune system “is always actively engaged,” said Brinkworth — it recalculates, reevaluates, and reorganizes itself all the time.

There are two parts to the immune system:

The innate immune system protects the body from pathogens in a nonspecific way. This includes immune cells, like phagocytes and mast cells, as well as the skin — which Brinkworth calls the “largest immunological barrier that you have.”

The adaptive immune system includes T and B cells. When this part of the immune system encounters a specific pathogen, it produces an initial immune response, and it remembers. If the body runs into this pathogen again, the immune system will respond more quickly and dramatically.

There are also steps you can take to boost your immune system, including eating a nutrient-rich diet and getting adequate sleep.

What weakens the immune system?

Some things can weaken the immune system, including:

“Immunity is the most expensive system we have. It costs a lot of calories,” said Brinkworth. “So it’s not very surprising that in endurance athletes and people who are doing extreme workouts, we see a down-regulation in immune function.”

Brinkworth said that when the body is under stress — like during calorie restriction — it can turn down the adaptive immune response in order to save energy.

“You can make the argument that some of the stuff that Hof is suggesting is dangerous,” said Brinkworth, “because it would potentially lead to this drop-down in adaptive responses if you did it persistently.”

Read more: Treating pain with heat and cold.

Taking a more moderate approach to physical activity can have many benefits.

“Why should we go to the extreme when we just need to engage in exercise?” says Ellen Glickman, PhD, a professor of exercise physiology at Kent State University, and a self-professed “moderation person.”

The Centers for Disease Control and Prevention (CDC) recommends adults get at least 150 minutes of moderate-intensity aerobic exercise per week, and 2 days or more of muscle-strengthening activities per week.

The CDC says physical activity can help lower your risk of diseases (such as type 2 diabetes), control your blood pressure, and stay at a moderate weight.

Glickman says aerobic exercise can be “equally engaging” and offers many benefits, such as boosting cardiovascular health, improving overall health and well-being, burning calories, and increasing endorphins.

Spending time outside, not just in extreme conditions, can be beneficial. Natural settings may improve short-term memory, relieve stress, reduce inflammation, and help you focus.

Read more: How long to get in shape?

That depends on who you ask.

“Evolution shapes health. Health is the outcome of evolution,” says Brinkworth. “That’s absolutely true.”

She stresses that evolution should definitely guide how we treat diseases and help people stay healthy, “but it needs to be done informed with real biological information.”

Other scientists wonder whether living like early humans makes sense from an evolutionary perspective.

Kyle Summers, PhD, an evolutionary biologist at East Carolina University, told Healthline that, while “substantial” change occurred to the human genome during the Pleistocene period, “there is also likely to have been a significant amount of evolutionary change during our more recent evolutionary history, including the 10,000 years or so since the origins of agriculture.”

Summers says it’s also challenging to know exactly how early humans lived.

Environmental conditioning has its proponents, but others caution a healthy dose of skepticism.

“While I think ideas from the Paleo community may have some merit in some contexts, it is hard to separate the valid ideas from those that are too speculative and unsupported,” says Summers.

There’s also the risk of going too far. Being too much like a Paleo human may not be all that it’s cracked up to be.

“If you want to be living in rough circumstances and deliberately stressing yourself long term and avoiding modern medicines and modern concepts of hygiene,” says Brinkworth, “you’re going to have the same lifespan as other members of the [early] Homo genus — that’s 30 to 35 years.”

Environmental conditioning is the idea that humans adapted to survive in the extreme conditions of early humankind. By recreating some of those conditions, such as exposing yourself to extreme cold, some people argue you can reap certain health benefits and boost the immune system.

However, there’s little research into environmental conditioning, and most studies that have been done relied on a small sample size of participants.

There’s a more robust body of science that shows taking a more moderate approach to physical activity has many benefits.