Energy Metabolism: Function, Tasks, Role & Diseases

The body’s energy metabolism is characterized by the biochemical breakdown of energy-rich organic parent compounds into energy-poor inorganic compounds with the release of energy. This energy is required to maintain biological processes. Furthermore, a distinction must be made between energy metabolism and building metabolism (anabolism).

What is energy metabolism?

Energy metabolism is characterized by the release of energy to ensure bodily processes. Every organism is subject to both energy and building metabolism. Energy metabolism is characterized by the release of energy to ensure bodily processes. In contrast, building metabolism involves building up the body’s own proteins, nucleic acids, fats and carbohydrates. Energy is necessary to maintain biological processes. A living being must supply energy from the outside in order to exist at all. Plants convert solar energy via photosynthesis into the chemical energy of carbohydrates, fats and proteins. Animals and humans need the chemical energy of these substances to sustain life. Mainly carbohydrates and fats are used by humans for energy production. Amino acids and proteins also have a high energy content. However, they are mainly needed to build up the body. The energy metabolism of humans ensures the basal metabolic rate and the power metabolic rate. The basal metabolic rate comprises the energy consumption for all vital energetic processes that are necessary in a state of complete rest. The power metabolism describes the additional energy consumption during physical activity.

Function and task

Human nutrition serves, on the one hand, to maintain physical functions and to provide additional power during physical exercise. On the other hand, the body’s own substances (proteins) are built from the building blocks of nutrients (mainly proteins). Carbohydrates and fats are the main sources of energy. Only when there is an insufficient supply of food can proteins also be used to produce energy. This is the case, for example, in a state of hunger (starvation metabolism). However, energy production from proteins may also be necessary as part of normal metabolism (with increased protein intake). Carbohydrates serve as short-term energy suppliers. After a carbohydrate-rich diet, blood glucose levels rise. As a result, there is increased insulin production. Insulin ensures that blood sugar is distributed to the individual cells. There it is broken down into carbon dioxide and water as part of the energy metabolism. During this breakdown, the chemical energy stored in the carbohydrates is simultaneously released to maintain bodily processes. Thus, when carbohydrates are burned, heat is generated and muscular activity is realized. In the liver and muscles, excess carbohydrates are stored again as glucogen. Glucogen is a starchy complex carbohydrate. When energy intake is too low, these carbohydrate stores are first called upon for energy production. Other energy suppliers are fats and fatty acids. Fats have an even higher energy content than carbohydrates. For example, one gram of sugar contains 4 kilocalories. In a gram of fat, however, there are already 9 kilocalories. Fats are responsible for the longer-term energy supply. When carbohydrates are used up, fat stores are tapped for energy. Fats are usually formed from too much supplied carbohydrates and fats. In the course of evolution, the organism has found a way to accumulate stores in the form of fat during periods of hunger. In times of abundance, more was consumed than was currently necessary in order to be able to store the excess energy. Proteins can also serve as energy suppliers. For example, when carbohydrate stores are depleted, the body’s own proteins are first broken down to amino acids to a greater extent. These, in turn, are then converted into glucose in a process known as gluconeogenesis in order to maintain blood glucose levels. Some bodily processes initially run only with the help of carbohydrates. Brain activity, for example, depends on a supply of glucose. If the blood glucose level drops dangerously, it can lead to unconsciousness. Even under extreme rest conditions, the body consumes energy.For example, the body temperature must be kept constant. Furthermore, all vital processes such as heart activity, breathing or brain activity continue. The resting metabolic rate is different for each person. Men usually have a higher basal metabolic rate than women because of their larger muscle mass. As a rule, it is 2000 to 2400 kilocalories for adults. The power metabolic rate then results from the additional physical exertion. It is not only the additional exercise that consumes energy. Heart activity, breathing and other processes are also stimulated during physical activity and have a greater energy requirement.

Diseases and ailments

If long-term imbalances in energy metabolism occur, diseases can result. These diseases originate when there is a mismatch between energy requirements and energy intake. In earlier times (and to some extent still in other areas of the world), many deaths occurred during periods of starvation. The energy demand could not be met because there was not enough food. When the energy reserves built up by the body were used up, the organism had to fall back on the body’s own proteins in the form of muscles. When these were almost depleted, the organs themselves were also depleted, eventually leading to multiple organ failure. At present, there is another circumstance which, although it does not lead to death so quickly, can produce serious diseases. Due to the abundant supply of food, overeating often occurs in modern times. More calories are supplied than consumed. The consequence is an increased storage of body fat, which in the long term can lead to diseases such as diabetes mellitus, arteriosclerosis or cardiovascular diseases with all their consequences. In addition to these diseases, the number of rheumatic diseases and cancer is also increasing. To avoid civilization diseases of this kind, a healthy lifestyle with plenty of exercise and a balanced diet is recommended.