Thermogenesis is the production of heat in the body, as done in thermoregulation to maintain body temperature. Thermogenesis occurs either in muscle or in brown adipose tissue. Decreased and increased thermogenesis can have serious consequences for the body.
What is thermogenesis?
Thermogenesis is the production of heat in the body, as done in thermoregulation to maintain body temperature. The human body is constantly in heat exchange processes with the environment. These processes are called thermoregulation and ensure the constancy of body temperature. The constant body temperature provides ideal working temperatures for the body processes. In strongly changing high and low temperatures, for example, the blood could no longer flow and the body tissues would die due to a lack of oxygen. To maintain a constant body temperature, for example, the higher the outside temperatures are, the more heat a person breaks down. Similarly, he produces heat when it is cold outside. The body’s heat production is known as thermogenesis and takes place primarily as part of metabolic processes. For example, heat is inevitably produced as a byproduct 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 body temperature.
Function and task
Many animal species have specialized mechanisms for thermoregulation. Heat production usually corresponds to either muscular and biochemical thermogenesis. In skeletal muscles, heat is generated during work, increased muscle tone, and cold shivering. Rarely does the efficiency of skeletal muscle exceed 20 percent. Therefore, most of the energy from physical work is converted to heat. In the body, this results in heating if the heat is not released. If you tense your muscles in a cold environment and thus raise muscle tone, you generate heat in the body. This principle is crucial for the cold shivering of thermoregulation, which protects the organism from cooling down to a certain extent. The visible trembling of muscles is characteristic of high muscle tone. Cold shivering is automatically initiated by the brain in cold environments to maintain body temperature despite the cold. The activated muscles contract, with simultaneous contractions of agonist and antagonist muscle groups. In physiological movements, simultaneous activation of agonists and antagonists is inconceivable under other circumstances. The thermal power achieved by cold shivering can range from 320 to 400 watts. This value is approximately five times the value of the basal metabolic rate of heat. From an energy point of view, real cold shivering is hard work and can therefore be sustained for a maximum of two hours. Biochemical thermogenesis must be distinguished from this muscular heat generation. At rest, humans generate a basal metabolic rate of body heat as part of basal thermogenesis. When the metabolic rate increases, thermogenesis occurs. Therefore, when necessary to maintain body temperature, the body burns additional fatty acids to generate 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 brown adipose tissue by strong cold stimuli. This type of heat production must be distinguished from postprandial thermogenesis, which occurs during digestion. Energy is used for food intake, breakdown, transport and storage of nutrients. The basal metabolic rate of heat is increased to maintain body temperature immediately after food intake. All types of thermogenesis are an important means of adapting to changing external temperatures. Cold shivering, and thus muscular thermogenesis, is initiated most rapidly after a drop in temperature. Biochemical processes take a longer time to adapt to falling temperatures.
Diseases and ailments
Decreased thermogenesis activity may promote obesity.A lowered basal metabolic rate usually characterizes the energy consumption of overweight people. This low turnover is largely genetically determined. However, reduced thermogenesis due to a lack of physical activity is an equally decisive parameter. The basal metabolic rate of the human body is closely related to muscle mass, which is also referred to 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 at rest. In this respect, building muscle mass always helps to burn fat. Similarly, lack of exercise, even at rest, favors a decreased basal metabolic rate with low thermogenesis. The extent to which people with pathological obesity have reduced thermogenesis due to nutritional factors has not yet been conclusively determined. Cold thermogenesis has now been discovered as a means of the weight loss industry. In addition to increasing fat burning, targeted cold exposure and the thermogenesis it induces can improve the immune system, increase hormone balance, lower blood sugar, and reduce cravings. Cold showers, cold baths and even ice baths have already been experimented with in this context. Thermogenesis also plays a role in diets. For example, improper diets can decrease thermogenesis activity. Disturbances of thermogenic processes can also be detected in the context of many metabolic disorders or thyroid diseases. Increased thermogenesis is present, for example, in the context of hyperthyroidism. In addition to an increase in the basal metabolic rate, an increase in body temperature occurs in this disease. Sweating and hypersensitivity to heat characterize the clinical picture. Analogously, in hypothyroidism there is a reduction in thermogenesis. Basal metabolic rate and body temperature are decreased. Sensitivity to cold and a worsened ability to adapt to temperature changes may be concomitant symptoms in patients with hypothyroidism.
