The daily caloric requirement depends on three different components:
- basal metabolic rate (MB O MBR from English " basal metabolic rate ")
- TID: food-induced thermogenesis (also called dynamic-specific action of foods)
- Physical activity
The percentage contribution of these components is shown in the image to the side.
BASAL METABOLISM: represents the amount of energy used in conditions of thermal neutrality, in the awake subject, but in conditions of total physical and mental relaxation. And higher in men than women, it falls with age and is directly linked to the lean mass of the subject.
TID: represents the energy spent by the body to digest, absorb and use the food introduced with the diet.
The TID varies according to the type and quantity of macronutrients as shown in the following table
| macronutrient | Grassi | Carbohydrates | Protein | Alcohol |
| TID (%) | 0-3% | 5-10% | 20-30% | 10-30% |
| The presence of dietary fiber in the diet reduces TID due to slowed absorption. | ||||
| Source: | Acheson KJ, 1983 Westerterp KR, 1999 | |||
In a balanced diet the TID represents about 10% of the total energy expenditure.
Diet-induced thermogenesis is distinguished in:
optional, which concerns the quantity of foods eaten and involves the activation of the sympathetic nervous system;
mandatory, which represents the energy spent on the use of individual nutrients (digestion, absorption, transport, metabolism, storage)
PHYSICAL ACTIVITY: every movement of the body induced by skeletal muscles able to give rise to an energy expenditure in excess of the rest condition.
The energy cost of physical activity depends on the frequency and intensity of the activities performed.
It can vary from about 15% for sedentary lifestyles, up to 3 ÷ 4 times the basic metabolism for very heavy occupational activities or for some athletes.
Physical exercise involving considerable muscular effort, at least according to some authors, would seem to keep energy expenditure high for long periods of time (up to 24 hours after the suspension of the activity).
Energy expenditure from physical activity varies in relation to:
- kind of activity
- intensity
- duration
- body mass
Calculate online calorie consumption of sports and non-sports activities: Calorie consumption calculator e
THERMOGENESIS FROM OTHER CAUSES: The thermogenesis induced by the smoke of a pack of cigarettes is on average 150 ÷ 200 kcal; the thermogenic effect of nicotine occurs within a few minutes of the start of cigarette smoking.
Nervines, some spices and catecholamines also have a thermogenic effect; the opposite effect is instead digital and beta-blockers. Finally, cold is also an important thermogenic stimulus mediated in humans by activation of the sympathetic system and by catecholamines.
