Author Nenah Sylver, Ph.D.

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Excerpts from the Holistic Handbook of Sauna Therapy:

Table of Contents and Index

History of Sauna Therapy

Sauna and Alkalization

Sauna and Weight Loss

Sauna and Fever

Sauna and Pesticides, Heavy Metals

Sauna Building Materials

Sauna Clinic and Spa Locations







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335 Pages, $34.95   

The Holistic Handbook of Sauna Therapy
By Nenah Sylver, Ph.D. 
335 Pages, $34.95

Body Heating and Weight Loss

Sauna manufacturers and dealers frequently claim that sweating causes weight loss. The promotional material from various companies ranges from modest to extravagant. The most conservative estimate states that a 20-minute to 30-minute sauna session—providing the person perspires consistently—yields a loss of 200 to 300 calories, an energy expenditure roughly equivalent to running two or three miles. The most extraordinary claim gives a 2000 calorie loss, roughly equivalent to the energy expended by someone in superb physical shape rowing or jogging for 30 minutes.

Some medical doctors scoff at even the more conservative figure. They declare that all weight lost during a sauna session is from water rather than fat, and that once the bodily fluids are replenished, the weight will immediately return. It is understandable that one might be skeptical of

manufacturers’ claims—especially if they sound extravagant. But at the same time, assertions from uninformed doctors who are antagonistic to the mere mention of sauna therapy are not reliable, either. Thus, we need to piece together the truths in these two contrasting views to determine whether or not people really lose weight from doing sauna therapy. Perhaps the most concise claim as to why one loses weight in the sauna is from Major Ward Dean in his letter to the editor in the August 7, 1981 issue of the Journal of the American Medical Association. Many sauna manufacturers cite this issue of the journal when referring to the number of calories expended in the sauna.

The fact overlooked by most people who attempt to debunk saunas and other devices that cause enhanced sweating is that the water does not just “leak out” of the body. Sweating is a part of the complex thermoregulatory process of the body involving substantial increases in heart rate, cardiac output, and metabolic rate, and consumes considerable energy. In a sauna . . . the only means of maintaining body temperatures in the normal range is by evaporation of sweat, a process that consumes approximately 0.586 kcal per gram of water lost. A moderately conditioned person can easily “sweat off ” 500 g[rams] in a sauna, consuming nearly 300 kcal [calories]—the equivalent of running 2 to 3 miles. A heat-conditioned person can easily sweat off 600 to 800 kcal with no adverse effects.

While the weight of the water lost can be regained by rehydration with water, the calories consumed will not be....Regular use of a sauna may impart a similar stress on the cardiovascular system [as running]—and its regular use may well be as effective a means of cardiovascular conditioning and burning of calories as regular exercise.12 [emphasis added] [For the sources of the information on cardiac output, the writer cites T.H. Benzinger, “Heat regulation: Homeostasis of Central Temperature in Man” in the Physiology Review 49 (1969): 671-759 and J.R. Brobeck, editor, Best & Taylor’s Physiological Basis of Medical Practice, 9th Ed, 1973, p. 133. For the sources of information on metabolic rate, the writer cites G.T. Koroxenidis, J.T. Shepherd, and R.J. Marshall, “Cardiovascular Response to Acute Heat Stress” in Journal of Applied Physiology 16: 869-872 and L.B. Rowell, G.L. Brengelmann, J.A. Murray, et al., “Cardiovascular Responses to Sustained High Skin Temperature in Resting Man

If an increase in metabolism can augment the amount of body heat that is produced, then conversely, given enough heat, the body can—and does—increase its speed of metabolism. Thermal and chemical messages in the body are intertwined in a process called chemical thermogenesis; and these processes are supported by the laws of thermodynamics. The following data, from a very interesting British textbook with the deceptively bland title of Clayton’s Electrotherapy 10E, explain why. (The numerous contributors to this book explain cellular function on many levels—physiological, biochemical, electromagnetic—to provide an understanding of the success of different non-invasive treatments, including heat, laser therapy, ultraviolet and far infrared therapies, electrical stimulation, and ultrasound.)

“When heat is added to matter,” writes Kenneth Collins, “a number of physical phenomena result from increasing the kinetic energy of its microstructure. [Kinetic energy is energy in motion.] These may be summarized as follows:”

  1. Rise in temperature: The average kinetic energy of constituent molecules increases.
  2. Expansion of the material: Increased kinetic energy produces a greater vibration of molecules which move further apart and expand the material. . . .

  3. Change in physical state: Changing a substance from one physical state (phase) to another requires a specific amount of heat energy. . . .

  4. Acceleration of chemical reactions: Van’t Hoff ’s Law states that “any chemical reaction capable of being accelerated, is accelerated by a rise in temperature. . . . 13

These natural laws point to the changes in body chemistry and the expansion of blood vessels that induce other changes that occur during fever, exercise, or saunas. Some increase in metabolism does occur in the body when it is subjected to high heat. We already know that the metabolic rate rises about six percent for every degree Fahrenheit rise in the body temperature. With the adipose (fat) cells heated at high enough rates to cause substantial molecular friction, the enzymes and hormones will break them down and transport them through the bloodstream for the body to use as energy. The more energy burned, the more weight the person loses.

Despite the above data, it must be emphasized that the results of heating the body from an external source are not identical to results from an internally generated fever. In fact, the two modalities might be seen to operate on opposing principles. Dr. William MacKay, Associate Professor in the Department of Physiology at the University of Toronto, explains:

During fever, the hypothalamus deliberately elevates the core body temperature and keeps it there. In the sauna, where the body temperature is elevated by external heat application, the hypothalamus is unwilling to allow a significant rise in core body temperature. As body temperature rises in the sauna, thermoreceptors in the hypothalamus detect the rise in temperature. In response, the hypothalamus activates mechanisms to cool the body—that is, keep the body temperature at its normal level. These mechanisms include skin vasodilation and sweating, of course, but also a reduction in secretion of hormones that increase metabolic rate. 14

This reduction in metabolic hormones, including thyroxin from the thyroid, helps clarify why people might not necessarily lose weight from sauna therapy. “However, one also has to contend with the fact that all metabolic reactions are sensitive to temperature,” MacKay points out. “The higher the temperature, the faster all metabolic reactions proceed. So just by temperature effects alone, metabolic rate will be elevated; although because of that the endocrine system will be trying hard to slow metabolism down. It is classic homeostasis at work.”15 As I will discuss later in this chapter, according to Dr. MacKay, during a fever, the body can switch from burning glucose to burning fat for energy. Although one probable reason for this is the starvation of microbes (most of which feed on glucose), conceivably one might also lose that extra abdominal bulge. But there is no guarantee that this will happen. This points to the wisdom of doing some form of aerobic exercise shortly before entering the sauna.

Despite the above, there is a very interesting study called “Repeated Thermal Therapy Improves Impaired Vascular Endothelial [lining of the blood vessels] Function in Patients with Coronary Risk Factors,” which strongly supports weight loss during sauna bathing (without exercise). Authors M. Imamura and colleagues were not exploring weight loss per se, but instead wanted to find out whether sauna therapy helps repair the cells lining the major blood vessels of the heart (it does). However, they also incidentally discovered that after 15 minutes of sauna therapy every day for two weeks, their subjects not only had a significant decrease of body weight, but their fasting blood sugar levels also decreased significantly. A lower fasting blood sugar level means that when the person awakens, the level of glucose in his or her blood is lower than usual. I attribute this lower reading to the increase in metabolism. The body burns fuel more quickly, which depletes some of the glucose that normally circulates through the blood to feed the tissues. (The heat source in this sauna used far infrared heating, which will be discussed in detail in Chapter 4.) Since the authors were not biased toward reporting weight loss but instead were looking for something else entirely, their finding assumes even more significance.

How much cold is applied after the body is heated, and even the degree of chill, may also affect weight loss. In an article called “How the Sauna Affects the Endocrine System,” K. Kukkonen-Harjula and K. Kauppinen studied the effects of sauna bathing on the increase of thyroxin (the thyroid hormone which increases the body’s metabolic rate) and TSH (thyroid-stimulating hormone, which the pituitary gland secretes to induce the thyroid gland to secrete more thyroxin). The authors write that if one gradually cools at room temperature following a sauna, there is no increase in these hormones. However, they write, “If the sauna is followed by cold exposure (a shower or a swim), the concentration of TSH is increased.”16 (Please note that this procedure is not safe for everyone, especially for those with a heart condition. Read Chapters 6, 7, and 8, and check with your doctor, before undergoing sudden extremes of heat and cold.)

“There is no question that cold-sensitive thermoreceptors are much more powerfully stimulated by rapid cooling than gradual cooling,” concurs MacKay. “The stronger sensory signal would then elicit a more vigorous response from the hypothalamus to activate the thyroid. So I would agree that the net stimulus to the thyroid is more powerful with rapid cooling. Indeed, one might conjecture that this aspect of sauna therapy may be the most important for aiding weight loss.” 17

A final explanation for weight loss during body heating may be due to the beneficial heating of a critical enzyme called 5’-deiodinase. The thyroid gland is responsible for regulating the body’s metabolism through its output of thyroxin (also known as T4). However, it is not T4 that is actually absorbed and utilized by the cells, but the physiologically more active hormone called liothyronine (or T3). The body uses the 5’-deiodinase enzyme to convert T4 to T3. Metabolic processes occur correctly only when this conversion takes place.

Significantly, though, T4 cannot be converted into T3 if the body temperature is too much below normal (98.6°F or 37°C). The shape of an enzyme depends on its temperature: too much continual heat makes the enzyme too tight, and too much continual cold makes the enzyme too loose. Due to chemical insult, dietary indiscretions, emotional trauma, or other stress, some people’s body temperature—and hence enzyme temperature— becomes too low to convert the thyroxin to liothyronine. (This condition is called Wilson’s Thyroid Syndrome, named after the doctor who discovered it.) People with Wilson’s Thyroid Syndrome are in a vicious cycle. If the body temperature is too low, the enzyme becomes too loose and the body cannot readily convert T4 to T3. This can make the body temperature even lower, which in turn makes the enzyme even more misshapen and more unable to perform the proper conversion of T4 to T3! One can have an adequately functioning thyroid gland, with lab tests that show sufficient T4 in the bloodstream—yet have low thyroid activity in the cells (indicated by tests for T3 levels), which is a truer indicator of metabolic function. Low T3 levels indicate low thyroid system (as opposed to low thyroid gland) function. A person can experience clinical symptoms of hypothyroidism due to low performance of either the thyroid gland, or of the thyroid system.

The treatment of choice for Wilson’s Thyroid Syndrome consists of a drug containing only T3 (rather than T4, or a combination of T3 and T4). Once the extra T3 in the body starts increasing the temperature, the 5’-deiodinase enzyme resumes more of its proper shape and starts converting more T4 into T3. With the resulting higher body temperature, the enzyme functions even more efficiently and a normal temperature is eventually reached— at which point (according to Wilson’s findings) the person no longer needs T3 medication. Since Wilson’s Thyroid Syndrome is a temperature-related condition, it seems clear that in addition to the effects of the (necessary) exogenously administered T3, heat from a sauna might conceivably warm the 5’-deiodinase enzyme enough to raise the metabolism at least a bit (which would assist with weight loss). A far infrared sauna is best for this function, for reasons that will be explained throughout this book.

Thus, many factors are involved in weight loss during body heating. Clearly, the weight loss discussion is complex and unresolved. It does not appear that there is any simple “yes” or “no” answer.


This book offers patients and practitioners life-saving information not available anywhere else in print or on the internet. If you would like to learn more about the book before ordering it, feel free to browse these excerpts, which are available online, free of charge:

Table of Contents and Index  History of Sauna Therapy  Sauna and Alkalization

Sauna and Weight Loss  Sauna and Fever  Sauna and Pesticides, Heavy Metals

Sauna Building Materials  Sauna Clinic and Spa Locations



The Holistic Handbook of Sauna Therapy
By Nenah Sylver, Ph.D.
Paperback Book, 335 Pages, $34.95

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