What is brown fat? What functions does it perform? We will answer these and other questions in the article. In the human body there are two types of fatty substance: brown (BAT - due to the burning of fat provides thermogenesis and creates heat) and white (WAT - is intended for energy storage). In obese people, as a rule, there is less brown fat, and more white.
Function
Brown fat allows the body to maintain a constant temperature. This mechanism is called thermogenesis. Two types of thermogenesis are distinguished: contractile (shivering), in which heat is generated due to contraction of skeletal muscles (a common occurrence is muscle tremor), and non-contractile (brown fat activity).
To effectively combat some ailments, the human body independently raises the temperature. If someone suffers from a fever, his thermoregulation system quickly reorganizes, activates and begins to act at a higher level. That is why body temperature up to 38.5 degrees should not be brought down.
Anatomy
First of all, brown fat was found in animals. In those animals that hibernate in the winter, this substance is best developed, since during this period the metabolism slows down. In view of this, it is not possible to maintain body temperature with muscle contractions.
Brown fat is also important when animals wake up in the spring: with the help of the heat generated by it, the body temperature increases significantly, due to which the beast wakes up.
The owners
Quite recently it became known that brown lard is present only in children. It helps them get used to the new environment after they are born. In newborns, this substance is located in the region of the kidneys, neck, along the upper back, on the shoulders, and makes up about 5% of body weight.
Also, in the body of infants, sometimes brown fat is mixed with white. For babies, the brown substance is of great importance, since it protects them from hypothermia, because of which premature babies often die. Thanks to this component, newborns are less sensitive to cold than older people.
Brown fat cells have a unique quality - they contain a huge number of mitochondria (organelles that contribute to the accumulation of energy). Thanks to them, they, in essence, have their own color. Mitochondria contain a specific protein UCP1, which, bypassing the level of ATP synthesis, instantly transforms fatty acids into heat.
The triglycerides (lipids) found in fat are the material from which heat (ATP) can be generated. When a baby needs a lot of energy (for example, to keep warm), fats undergo lipolysis. As a result, fatty acids appear, which UCP1 in brown lard cells transforms into heat. As a result, a decrease in body fat is observed. First, triglycerides are consumed in brown substance, and when lipid reserves begin to melt, then in harsh white.
As a result, the body reduces its weight. However, for the efficiency of the process, a baby who is born should have a good diet (energy is needed to activate lipolysis) and breathe normally (oxygen is required for the transformation of fatty acids).
Unfortunately, in an adult, this mechanism is gradually weakening. A couple of weeks after birth, a shiver (reaction to hypothermia) replaces the action of a brown substance, especially if the kids are warmly clothed and kept in a hot room.
Adults
Today it was discovered that brown fat in an adult person is available. For a long time, it was believed that this substance was losing its significance by the end of the first year of human life. However, in 2008, experts determined that brown adipose tissue not only resides in the body of adults (this became known back in 1908), but is also activated by cold.
This discovery was made using a new technology for visualizing active metabolism in tissues. We used emission positron and computed tomography, which showed that in the body of an adult individual there are about 20-30 grams (so little) of brown functional fat, mainly in the supraclavicular area.
PET-CT is known to fix the metabolic activity of tissue. Physiologist Wouter van Marken Lichtenbelt said a group of young people (24 people) were given the exact dose of radioactive glucose. This was done in order to further be able to detect active brown fat using a specific device.
After that, the participants in the study were brought to a room whose temperature did not exceed 16 degrees. A CT scan showed that under the skin of the chest, neck and abdomen of 23 people there is a fat “useful” tissue that works by warming people in a cold room.
The physiologist said that the specialists were very surprised to see that so many people have so much of it. When three participants were examined at room temperature, they did not find the brown substance. Experts believe that the tissue did not disappear, but simply stopped its work.
Efficiency
So, you know where a person has brown fat. It is equal to not more than 1-2% of body weight. And yet, when the sympathetic nervous system stimulates this tissue in supercooled mammals, accustomed to cold, it increases its heat production. The energy generated in this way can reach one third of all the additionally created heat in the body. When brown fat is activated, it spends up to 300 watts (some call it 400 watts) per kilogram of adult mass.
It is known that a person of average weight at rest burns about 1 kW of energy. By activating brown fat, you can lie on the bed and spend twenty times more energy than before.
Fat burning
What are the functions of brown fat? It helps eliminate fat. If activated, fatty acids from white adipose tissue are pumped into brown. The white substance is deposited in the capsules and glands of the internal organs, under the skin. Brown, instead of accumulating energy, burns it in huge quantities. As a result, heat is released. This process is called thermogenesis, which begins its work due to excessive food intake.
conclusions
White and brown fat are two different substances. The oxidizing ability of brown matter is 20 times greater than that of white. The thermogenin protein acts in brown tissue during thermogenesis, which promotes the separation of respiration and oxidative phosphorylation.
So, we found out what brown fat is. How to increase its amount in the human body to effectively fight obesity? To solve this problem, scientists use not only medicines, but also surgical means: they use liposuction to extract ordinary white fat, transform it into brown, and then implant it to a person.
Theoretically, in order to lose weight, you need to either increase the activity of the brown substance at ordinary temperature, or increase its amount, or perform the first and second.
Specialists from the Diabetes Association of the United States believe that brown fat contains very important reserves for patients with diabetes and obesity. It is also known that in a complete person, brown fat activity is suppressed, and its amount is reduced. Therefore, in the near future, the emergence of new drug and other methods of accumulation and activation of this "useful" substance in adults.