Sweating vs subcutaneous fat and weight loss.

Are obese people sweating more than those with ordinary body weight? What happens in different conditions of the surrounding? If we look for an answer, we will find it very fast, together with the answers for other questions. Enjoy the reading.

You should definitely read:

Why aren't we hungry during heatwave?

Human being is warm-blooded, it means that the body aims at sustaining average temperature of the body of 37 ± 0.5°C [1]. Body fat is differentiated – among other types, there is brown fat, subcutaneous fat (white), visceral fat (around inner organs).

Brown fat, paradoxically, is the biggest ally of humans, as it is usually an active tissue. It contains a lot of mitochondrion and it is supplied with loads of blood vessels. It means, that (just like muscle tissue) it “burns” energy! Unfortunately, there isn't much of this kind of fat in the human body [3]. The phenomenon of brown fat is explained by the latest research: “Dr Patrick Seale from the Medical Academy at Harvard University, together with his co-workers, informed in the “Nature” magazine, that brown fat derives from the progenitor cell belonging to the line of development of the scheletal muscles [3]. Whereas, viscular fat is the biggest enemy of health and shape – it causes insulin resistance, metabolic diseases, it increases the risk of type II diabetes. In the context of temperature and dehydration, we should be most interested in subcutaneous fatty tissue. For a growing number of people, such “ballast” is a nuisance. If you live outside the area of e.g. mountain climate, Siberia, Antarctica – excess amount of kilograms is unnecessary for you. There are a lot of studies proving that fatty tissue is not only unaesthetic, but it may also cause worse functioning of the whole body.

Fatty tissue and its influence on health

You should know that overweight aiming at obesity may lead to:

  • insulin resistance – worse tolerance of carbohydrates, larger building up of fatty tissue,

  • the more insulin there is in blood, the more fat there is in the body, because it intensifies the synthesis of fatty acids,

  • disturbed lipids (proportions of HDL, LDL, cholesterol, triglycerides),

  • lower level of testosterone (#1), one of the mechanisms is larger aromatization of testosterone to estrogen (similar phenomenon is crucial for many side effects occurring during using pharmacological doping of e.g testosterone or methandiendon),

  • lower level of testosterone (#2), by a mechanism of increasing the amount of SHBG (globulin binding e.g. testosterone) [2],

  • slower process of getting rid of fatty tissue (indirectly by the influence on the binding of thyroid hormones by SHBG),

  • larger inflammation in the body (TNF-alpha, cortisol, cytokines, e.g. IL-6) – why? Because these compounds are produced also in fatty tissue!

But that's not all!

Excess amount of fat = excess amount of sweat?

As I mentioned before, fat is a protective and isolating layer. However, in modern world, such a “luggage” can bring another sad side effect – excess amount of sweat. Why? Sweat is a hypotonic (0.3%) solution of NaCl. The mechanism of evaporation of the released sweat is the most efficient way of giving away the heat to the surrounding [3]. Sweating is some kind of defensive reaction of the body. According to J. Gorski's research in “The Physiology of Physical Training”: “the increase of the inner temperature by 1 Celsius degree means the increase of heart beat by 9 beats per minute and lower volume of ejection fraction of the heart by about 11ml” [5]. The body will do anything to get rid of the excess body temperature, because it's dangerous for health, or sometimes even for life. The thicker layer of fat – the worse process of removing heat from the body. The body produces heat at all times, even when it rests: “releasing heat by an adult healthy man staying in rest in the heat comfort zone is 4.184 kJ * kg of body weight-1 * h-1. As it's easy to count, a man weighing 70 kg staying in lying position without any movement releases about 293 kJ of heat per hour, i.e. about the same amount as an 80W light bulb” [3]. It is much more complicated in case of obese people who start physical effort, such as strength or aerobic training. For healthy people, training causes that metabolism is even 100 times faster, which results in fifteen to twenty times higher release of heat by muscles. More heat – greater fight of the body to bring homeaostasis back. The worse process of getting rid of heat – the more sweat. The more sweat – the larger loss of electrolytes – sodium, potassium, magnesium. Drinking water doesn't have to help, as the fluid has to be transferred from the digestive tract, which additionally stresses heart. And that's how the circle closes.

In unconvenient conditions (e.g. when it's hot), heart beats faster without any special stress than when it's cooler. Each additional degree of the inner temperature of the body increases that stress. But that's not all – intensive training of an obese person, even in perfect conditions, causes large loss of water and electrolytes: “Galloway and Maughan stated that in a cold surrounding (10ºC), the pace of sweating is 0.65 l/h for a person working out with the intensity of 80% of maximum intake of oxygen” [4]. “During physical effort, in normal conditions, sweat release within one hour is 1-1.5 l. On a hot, humid day this release increases to even 4 l / hour” [5]. According to J. Gorski, losing 1 liter of sweat is the cost of 580 kcal of heat.

What are the results of dehydration?

In one of the studies, the limits in consumed liquids resulted in horrible effects. The supply of fluids was limited on purpose during night and during physical effort, in order to investigate the results of dehydration among competitors. 9 men were riding bicycles for 90 minutes with the intensity of ~65% of peak oxygen intake. After that for 6 minutes there was the time trial (they released 6 kJ/kg of body mass then). After 20 minutes blood samples were gathered, and the samples of muscles were gathered before, after 45 and 90 minutes of workout.

  • The dehydration group started with the deficiency of 0.6% of body mass caused by limited supply of liquids at night, after 45 minutes the loss was 1.4%, after 90 minutes, it was 2.3%, and after the time trial it was 3.1% loss of body mass,

  • There were no differences in oxygen intake, production of carbon dioxide or the loss of sweat between the groups,

  • But such parameters, like heart rate (HR), the perception of the effort, inner temperature, the osmolality of plasma, volume of the lost plasma, the amount of the heat shock proteins (Hsp72) and using glycogen, as well as the oxidation of carbohydrates were larger in the dehydration group (when the volunteers reached the threshold from 0.6 to 2.3% of dehydration),

  • The time trial for the dehydrated was 13% slower, compared to the hydrated group (the volunteers from the liquid limit group started the trial at the threshold of 2.3% of dehydration and finished at 3.1%),

  • Even during work on low load, all the metabolic parameters were more adverse in the dehydration group (what's most shocking, there were more lactates in blood and muscles, as well as Hsp72 protein in blood serum!).

Final conclusions:

  • Excess amount of fatty tissue may lower the effort abilities of a competitor, especially during long-lasting effort in high temperature and/or humidity,

  • Obese people during the same physical effort will dehydrate more than the competitors with ordinary body composition,

  • Dehydration leads to further increase of heart rate and lowe effort abilities – concerning various metabolic parameters,

  • In order to optimize training, improve the hormonal environment and metabolic parameters, one should get rid of fatty tissue.

Final note – losing weight e.g. during intensive training in warm clothes, sitting in scorcher, going to sauna, liquid limitation, have NO influence on losing subcutaneous fatty tissue. This way you can lose kilograms of water, not fat. Such behavior is harmful for health and senseless. They only make sense for competitors of martial arts, who have to have particular weight for a particular moment in time. In general, those people are maximally trained without any body fat, so such actions are their last hope.

I developed this topic here: The weirdest ideas concerning “cardio” training

Sources: Wymiana ciepła między człowiekiem a jego otoczeniem http://archiwum.ciop.pl/6625.html] 2. "Endokrynologia wysiłku fizycznego sportowców z zarysem endokrynologii ogólnej" M. Mędraś. 3. Termoregulacja organizmu człowieka i obciążenie termiczne prof. dr hab. med. Mieczysław Krause 4. Ronald J. Maugham „Zapotrzebowanie na wodę i elektrolity – efekt wysiłku fizycznego” http://www.cos.pl/sw/34_04/43.pdf 5. J. Górski „Fizjologa wysiłku i treningu fizycznego": 6. Physiol Rep. 2015 Aug;3(8). pii: e12483. doi: 10.14814/phy2.12483. The effect of dehydration on muscle metabolism and time trial performance during prolonged cycling in males.