Your body needs energy for every activity, e.g. for breathing, digestion, circulation and movement. The energy turnover per day (daily requirement) is made up of the basic turnover and the output turnover.
The basal metabolic rate is the amount of energy that the body needs to maintain its body functions when it is completely at rest. There are various formulas for calculating the basal metabolic rate, including the Harris-Benedict formula, the Broca index adjustment and the Mifflin-St. Jeor formula.
With physical activity, of course, the energy requirement also increases. The performance turnover relates primarily to the muscle work performed. Since the daily muscle work performed varies greatly depending on professional activity and sporting activities, various PAL factors (PAL = Physical Activity Level) are classified for the calculation.
If you adjust your calorie intake to your personal and individual energy expenditure, your body weight will remain constant. If you take in less, your body weight will drop over time and you will lose weight. However, you should be careful not to eat below the basal metabolic rate, otherwise the body will run on the back burner. In addition to the fat reserves, the muscles in particular are then broken down. Another undesirable effect of losing weight in this radical way is the yo-yo effect.
The daily requirement depends, among other things, on gender, age, body size and body weight. However, many other factors also have an influence, such as outside temperature, physical activity and state of health. Therefore, it is very difficult to determine the exact value.