What is metabolism

Metabolism – a set of biochemical processes that occur in any organism – including the human body – and are aimed at ensuring vital functions. These biochemical processes influence our growth and adapting to a changing environment.

Anabolism and catabolism

Anabolism is called the creation of matter – a sequence of chemical reactions that build or synthesize molecules from smaller components. As a rule, anabolic reactions are accompanied by energy consumption.

Catabolism is the destruction of matter – a series of chemical decomposition reactions in which large molecules break down into smaller pieces. As a rule, the process proceeds with the release of energy.

Metabolism and body weight

Our weight is the result of “catabolism minus anabolism.” In other words, the amount of energy generated in our body (catabolism) minus the amount of energy that our body consumes (anabolism).

Excess energy is accumulated in the form of fat or glycogen (in the form of carbohydrates, energy is stored mainly in the liver and muscle tissue).

When one gram of fat is broken down, we lose 9 kcal, and when broken down by protein or carbohydrates – 4 kcal.

Although overweight is most often the result of the body accumulating energy in the form of fat due to its excess, hormones, or underlying chronic diseases sometimes affect metabolism.

Many people think that thin people are characterized by “accelerated metabolism,” while overweight or obese people suffer from a “slow metabolism.” In fact, chronic diseases such as hypothyroidism (low thyroid activity) are not the main cause of obesity. Weight gain is mainly associated with energy imbalance.

If you are overweight or obese, it is advisable to undergo a medical examination and make sure that the weight gain is not caused by endocrine or somatic pathology.

Energy needs

Body mass 

The higher is the body weight, the higher the calorie requirement we have. It is also true that people with a high ratio of muscle to adipose tissue need more calories than people with a similar total mass, but with a lower percentage of muscle tissue. Persons with a high muscle-fat ratio have a higher level of basal metabolism than people with a similar total mass, but with a lower muscle-fat ratio.


When we get older, we are confronted with factors that lead to reduced energy requirements. Our muscle mass is reduced, which leads to a decrease in the muscle-fat ratio. Our metabolism is gradually being rebuilt, which also entails a decrease in calorie needs.

The following age factors reduce our energy needs:

  1. Hormones – with age, less testosterone, and estrogen are formed in the body of men and women. Both hormones are involved in anabolic processes that consume energy. The synthesis of human growth hormone, which has a tremendous effect on anabolic reactions, also decreases with age. When we get older, the balance shifts from anabolic hormones to catabolic, which dramatically increases the predisposition to weight gain, and this is due to adipose tissue, not muscle;
  2. Menopause – in women, the production of hormones decreases, which causes the body to burn more energy. Most women find that losing weight during this period is very problematic;
  3. Physical activity – with age, people, as a rule, are not as active as they were in youth. This is explained not only by a more measured way of life. Most people who in their youth earned hard physical labor, after 45 go to sedentary work. This may be due to career advancement, which takes place in many sectors, for example, in the army, police, fire service, as well as retraining, transfer to a fundamentally different job or early retirement;
  4. Sex. Men have a higher level of basal metabolism than women, which is explained by a large percentage of muscle tissue in the male body. This means that the average man burns more calories than the average woman of his age with similar body weight.

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