The Thermogenesis is the production of heat in the body, as it is done during thermoregulation to maintain the body temperature. Thermogenesis takes place either in the muscles or in the brown adipose tissue. Decreased and increased thermogenesis can have serious consequences for the body.
What is thermogenesis?
The human body is permanently in heat exchange processes with the environment. These processes are called thermoregulation and ensure the constancy of body temperature. The constant body temperature offers the body processes ideal working temperatures. In high and low temperatures, for example, the blood could no longer flow and the body tissues would die due to a lack of oxygen.
For example, to maintain a constant body temperature, the higher the outside temperature, the more heat it dissipates. Similarly, it produces heat when it is cold outside.
The body's heat production is known as thermogenesis and takes place primarily in the context of metabolic processes. Heat, for example, inevitably arises as a by-product of energy metabolism, muscle activity and digestion. In this context, a distinction is made between muscular, biochemical and postprandial thermogenesis.
Depending on the ambient temperature, the heat produced during thermogenesis is either stored or released to maintain the body temperature.
Function & task
Many animal species have specialized mechanisms for thermoregulation. The heat generation usually corresponds to either muscular and biochemical thermogenesis. The skeletal muscles generate heat during work, increased muscle tone and shivering.
The efficiency of the skeletal muscles rarely exceeds 20 percent. The energy from physical work is therefore largely converted into heat. In this way, the body becomes warm if the heat is not given off. If you tense your muscles in a cold environment and thus increase your muscle tone, you generate heat in your body. This principle is crucial for the shivering of the thermoregulation, which protects the organism to a certain extent from cooling down.
The visible tremor of the muscles is characteristic of high muscle tone. Shivering is automatically initiated by the brain in a cold environment in order to be able to maintain the body temperature despite the cold. The activated muscles contract, whereby agonistic and antagonistic muscle groups simultaneously contract. In the case of physiological movement sequences, a simultaneous activation of agonists and antagonists is inconceivable under other circumstances.
The thermal output achieved by shivering can be between 320 and 400 watts. This value corresponds to about five times the value of the heat consumption. Real shivering is hard work in terms of energy and can therefore be endured for a maximum of two hours.
The biochemical thermogenesis must be distinguished from this muscular heat generation. In the resting state, humans generate a basal metabolic rate of body heat as part of the basal thermogenesis. When the metabolic rate increases, thermogenesis occurs. Therefore, when it is necessary to maintain the body temperature, the body burns additional fatty acids and thus generates heat in the liver and brown adipose tissue. Thermogenesis in adipose tissue is not linked to ATP synthesis and is therefore most effective. The activity of the heat-producing protein Thermogenin is initiated in the brown adipose tissue by strong cold stimuli.
This type of heat production is to be distinguished from postprandial thermogenesis, as it occurs during digestion. Energy is used to ingest, split, transport and store nutrients. The basal metabolic rate of heat is increased immediately after eating to maintain the body temperature.
All types of thermogenesis are an important means of adapting to changing outside temperatures. The shivering and with it the muscular thermogenesis is initiated the fastest after a drop in temperature. Biochemical processes need a longer changeover time to adapt to falling temperatures.
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A reduced thermogenic activity can promote obesity. A reduced basal metabolic rate usually indicates the energy consumption of overweight people. This low turnover is largely genetically determined. However, reduced thermogenesis due to lack of body movement is an equally critical parameter.
The basal metabolic rate of the human body is closely related to muscle mass, which is also known as fat-free mass. The more muscle mass there is in the body, the higher the basal metabolic rate of energy due to thermogenesis, even during rest phases. Building muscle mass always helps to burn fat.
Similarly, a lack of exercise, even during periods of rest, promotes a reduced basal metabolic rate with low thermogenesis. The extent to which people with pathological obesity suffer from reduced heat generation due to nutritional factors has not yet been conclusively clarified.
Cold thermogenesis has now been discovered as a means of the weight loss industry. In addition to increasing fat burning, targeted exposure to cold and the thermogenesis induced by it can improve the immune system, increase the hormone balance, lower blood sugar and reduce cravings. In this context, experiments have already been carried out with cold showers, cold baths and even ice baths. Thermogenesis also plays a role in diets. For example, wrong diets can reduce thermogenic activity.
Disturbances of the thermogenic processes can also be detected in the context of many metabolic disorders or thyroid diseases. For example, there is increased thermogenesis in the context of hyperthyroidism. In addition to an increase in the basal metabolic rate, this disease also causes an increase in body temperature. Sweating and hypersensitivity to heat characterize the clinical picture. Analogous to this, there is a reduction in thermogenesis in hypothyroidism. The basal metabolic rate and body temperature are reduced. Sensitivity to cold and a worsened ability to adapt to temperature fluctuations can appear accompanying symptoms in patients with hypothyroidism.
