Diet-induced thermogenesis

"Energy requirement and basal metabolism

Diet-induced thermogenesis refers to the extra energy that the body spends every time it takes food. Also for this reason, overweight people are often advised to divide their daily caloric ration into many small meals.

The energy expenditure linked to food thermogenesis corresponds, on average, to 10% of daily calorie consumption. It is given by two components: compulsory thermogenesis and optional thermogenesis.

A part of the energy expended is destined to the physiological and metabolic processes related to digestion,
to the "absorption and" processing of nutrients introduced with the diet (Compulsory Thermogenesis)

A part of the energy is expended as a consequence of the sympathetic nervous activation, induced, for example, by nerve substances (Facultative Thermogenesis)

The thermogenic effect of food varies according to the nutrients that constitute it:

Protides: they have by far the highest thermogenic value; the energy spent for the various processes described above amounts to 30% of the caloric intake provided by the proteins taken with food

Glucides: low thermogenic power (7% of the energy supplied)

Lipids: very low thermogenic power (3% of the energy supplied)

The thermogenic effect of proteins is higher than that of other nutrients, since the deamination of amino acids and the subsequent production of urea costs the organism a lot of energy.

Even the nerve substances, such as caffeine and related molecules (contained in tea, cocoa, guarana, etc.), have a moderate thermogenic power.

Physical activity

Physical activity is the most variable item of energy expenditure, as it depends on the individual's work habits and lifestyle.

Generally speaking, in a sedentary individual, the energy expenditure linked to physical activity corresponds on average to 30% of the daily caloric expenditure.

However, it should be borne in mind that the energy consumption linked to physical activity is closely related to the body mass of the subject. The greater this is, the higher the caloric expenditure associated with physical effort. This is obviously due to the greater energy demand necessary to move the high body size; moreover, it must be remembered that the adipose tissue acts as a thermal insulator, preventing the dispersion of the heat produced. Overweight people are therefore forced to spend more energy on eliminate the heat developed during physical activity.

Thermoregulation

Human beings are homeotherms, that is, they must keep their internal temperature within a fairly constant range of values. All this costs the body a lot of energy, necessary for: