Introduction

Many of us have ancestral roots from a tropical or subtropical region of the world, where sweating outdoors was a natural way of life. Now, due to modern life, we work indoors and even work out in temperature-controlled gyms. Our bodies have actually become more heat intolerant and this could be causing physiological and metabolic changes that prevent us from reaching the best possible health, body composition and fitness. In this post, we are going to take a closer look at whether heat exposure and sauna use helps burn body fat and improves health.

What Happens to Humans in a Sauna?

So first things first, what is actually going on in the body when a person sits in a sauna? Obviously the body heats up, but just how hot? After about 30 minutes in a sauna which is 174 degrees Fahrenheit, the skin typically heats up to about 105 degrees Fahrenheit. This starts compensatory cooling which the body attains through profuse sweating at a rate of 0.6-1 kilograms an hour. When a body sweats, it can give off about 200 watts of heat, which isn’t enough to offset the total heat load. As a result, the body’s insides begin to heat up. This sounds concerning right? Let’s look at how the body reacts.  After being exposed to a sauna regularly, the body adapts to the heat and is better suited to handle it. Ways in which this can be seen are as follows:

  • An enhanced cardiovascular system and lower heart rate.
  • Lowered body temperature when working out.
  • Increased sweat pace and sweat sensitivity as a role of increased thermoregulatory control.
  • Improved blood flow to skeletal muscles which is known as muscle perfusion.
  • Improved muscle perfusion reduces the rate of glycogen depletion.
  • Red blood cell count increase.
  • Oxygen transported to the muscles is increased.

Research on Sauna Use

There has been research conducted on sauna use in order to get real answers on the benefits. One study was performed to find out if sauna use had an impact on heart health. For over 30 years the health and sauna habits of 2,315 Finnish men around the age of 53 was tracked. The results showed an extraordinary protection from fatal heart attacks by sauna users.  

Researchers found that men using a sauna two or three times a week had a 23% lower chance of having a fatal heart attack, compared to men that used a sauna only once a week. Men that used a sauna four to seven times a week had a 48% lower chance of having a fatal heart attack compared to men that only used a sauna once a week!

Additionally, there are several studies that prove that the effects of heat stress can have powerful effects on growth hormone levels. One study from 1976 discovered that Finnish sauna usage increased growth hormone over 140%. Increasing growth hormone levels increases protein synthesis  (this includes muscle) and helps with fat loss.

Health Benefits

Several health benefits have been identified as resulting from sauna use. The following are some of the most common:

  • Lower Oxidative Stress – Oxidative stress is an imbalance between the load of reactive oxygen species in the body and the body’s ability to deal with them.  Oxidative stress is what leads to chronic health conditions like arthritis, heart disease, and cancer.  It also accelerates aging.  Exercise, getting enough sleep, proper nutrition as outlined in my book, meditation, and targeted heat stress can all help lower oxidative stress in both healthy and sick people. Sauna use additionally helps to relieve oxidative stress and keep it in balance.
  • Increase Antioxidant Capacity– After oxidative stress is increased, sauna therapy triggers compensatory adaptations and antioxidant defenses in the blood.
  • Improve Lipid Profiles– Using a sauna lowers LDL and triglyceride levels while increasing HDL in both men and women.
  • Help with Insulin Sensitivity– We want our bodies to be more insulin sensitive to reduce diabetes risk, heart disease risk and to help with body fat loss and it appears sauna use can help with this.  In addition, regular sauna use increases the expression of a powerful chemical called nitric oxide which relaxes blood vessels and improves blood flow, mimicking the changes seen from doing aerobic exercise.

Athletic Performance Benefits

As athletes use their bodies more than the typical person, there are additional benefits that they can reap with sauna use.

  • Endurance– Plasma volume and blood flow to the heart are increased with sauna use. This reduces cardiovascular strain so the heart rate is lowered, which increases endurance in trained and untrained athletes. Blood flow to skeletal muscles is increased and they stay fueled with glucose, esterified fatty acids, and oxygen. Additionally, by-products like lactic acid are removed. Increased nutrients delivered to the muscles helps to reduce their reliance on glycogen stores. Thermoregulatory control is improved, which operates by turning on the sympathetic nervous system and increasing the blood flow to the skin, thus increasing sweat rate.
  • Increased Blood Volume– Blood volume was increased by 7.1% in a particular study and the red blood cell count was increased by 3.5%. Increased blood cell count means more oxygen delivered to the muscles. The heat acclimation increases the red blood cell count through production of the hormone erythropoietin (aka EPO).  By the way, synthetic EPO is the illegal drug athletes like Lance Armstrong used to perform “blood doping” to improve their blood’s oxygen delivery.  Looks like sauna use and heat exposure are more natural (and legal) ways to derive a blood doping effect.  
  • Muscular Hypertrophy– Muscle hypertrophy is the increased size of muscle cells and possibly an increase in strength.

Hyperthermic training has become a key way athletes and even recreational fitness enthusiasts exercise to significantly improve performance.  Doesn’t always have to involve using a sauna.  Even exercising in heated conditions, like on a hot summer day (be sure to adequately hydrate) can get you some of these benefits and perhaps this explains some of the additional benefits from heated yoga techniques popularized by Bikram yoga.

Kinds of Saunas

When deciding to use a sauna, you have a few options. The following are the most commonly found:

Dry saunas are the most conventional and widely known form of sauna, using entirely dry heat. They are usually between 160-194°F and are the ones that researchers have focused on so far. On the other hand, a sauna with steam raises body temperature more than dry saunas, but it might be hard to stay in long enough to get the same benefits.

An infrared sauna uses an infrared lamp to heat your body to precisely the temperature desired. The temperatures are much lower, about 120-130 °F. Waon is an infrared sauna therapy used in Japan to treat heart failure, cardiovascular disease, and fibromyalgia. It may also help improve exercise tolerance and improve wound healing.

Precautions

There are a few precautions to keep in mind before entering a sauna, as it does put your body under stress initially, which may not be suitable for everyone. First, never drink alcohol or take drugs before going into a sauna, it significantly increases your risk of dying. Also, patients with Multiple Sclerosis may have problems with cognitive function and motor control for about an hour after using a sauna.  Avoid sauna use during pregnancy.  If you have any chronic health conditions or are at high risk for heart disease, it is best to get clearance from your doctor before implementing regular sauna use.  

Be Careful! Heat stress is very taxing so if you think you’re getting too warm, you should probably get out. Heatstroke can happen quickly and without warning. Keep a refreshing drink available, something like coconut water, mineral water, or even regular water with a pinch of sea salt to replenish some of the lost minerals from sweating.  

Other Ways to Improve Heat Tolerance

Even if the sauna is not for you, trying to gradually increase your heat intolerance with exercise/activity looks like it carries benefit and mimics the type of activities our ancestors performed.  My grandmother did quite a bit of her housework out in the Kolkata, India summer heat.  Even taking your laptop or smartphone outside on a hot day to do some essential work might be a way to already start ramping up your heat tolerance.

Also keep in mind that your skin is one of your most potent organs for detoxification.  We are exposed to so many chemicals in our foods, through the use of skin care products, BPA-laden packages and food containers, and through the air we breathe, that sweating these out intermittently is a great way to improve health.  BPA (Bisphenol-A) is a ubiquitous contaminant known as an “endocrine disruptor” which interferes with our body’s hormonal balance.  It’s found in everything from kid’s toys, plastic containers, receipts and pizza boxes (read this for surprising sources).  Studies analyzing sweat samples have detected toxins and metals including cadmium, mercury, lead and BPA.  So don’t look at sweating as a nuisance.  It may be an essential way for your body to purge itself from at least some of the unavoidable toxins of modern day living.   Especially if you live in or visit an area of the world where pollution is a major problem, you may need to incorporate some sweat-induced detoxification sessions.

Vitamin D Deficiency: Another Metabolic Consequence

In addition to heat intolerance, many of my Indian and Asian patients are especially sun intolerant, worrying about the societal stigma of a darkened complexion.  Whereas tanned bodies are considered exotic in Western countries, it’s quite the opposite in South Asian and East Asian cultures.  Sun exposure and perspiration are delegated to laboring classes, not to the affluent.  Unfortunately sun avoidance leads to another major metabolic issue that compounds the heat intolerance effects we discussed, and that is severe vitamin D deficiency, which I discuss in detail here.  Unless you have serious risk factors for sun-induced skin cancer, intermittent and safe sun exposure is a critical way to boost vitamin D levels. 

Hopefully this information gives you a new perspective on your summer trips to India, East Asia, or some hot tropical destination.  Don’t confine yourself exclusively to indoor air conditioned spaces. I want you to reframe hot, sunny days from being a calamity, to an ideal opportunity for you to switch on some highly advantageous metabolic adaptations that may potentially help improve body composition, athletic performance, detoxification and prolong life.  Now go out and enjoy the sun and heat!