Energy expenditure

 Components of energy expenditure

- Basal metabolism, or energy needed to maintain essential physiological functions, including growth, pregnancy, lactation, ...

The minimum amount of energy required to maintain vital functions and which is used primarily in active transport processes, involved in various functions such as cardiorespiratory activity, excretion, maintenance of body temperature, extension and transmission of signals, maintenance Muscle tone, ... as well as in biosynthesis processes of molecules.

Its measurement is carried out in the following conditions:

• Physical rest, in supine position, without muscular movements, having not performed exercise 30-60 min before. The subject should not be asleep, since during sleep the basal metabolism decreases by 10%. • Mental rest, the subject should not be subjected to emotions, noises, ...
• Adequate environmental conditions, temperature of 20-25 ° C, since at this temperature the heat produced at rest is sufficient for the maintenance of body temperature.
• Fasting, the last meal should have been done 8-12 hours earlier.

WHO formulas

 Man

• 0-3 years: 60.9 x weight -54
• 3-10 years: 22.7 x weight + 495
• 10-18 years: 17,5 x weight + 651
• 18-30 years: 15.3 x weight + 679
• 31-60 years: 11.6 x weight + 879
•> 60 years: 13.5 x weight + 487

Woman

• 0-3 years: 61 x weight -51
• 3-10 years: 22.5 x weight + 499
• 10-18 years: 12.2 x weight + 456
• 18-30 years: 14.7 x weight + 496
• 31-60 years: 8.7 x weight + 829
• 60 years: 10.5 x weight + 59

- Formula of fast estimation:

24 Kcal / hour / kg of weight
♂MB = 1.0 kcal / hr / kg
♀MB = 0.9 kcal / hr / kg

- Original equations of Harris-Benedict (1918-1919):

♂ MB = 66.47 + [13.75 x weight (kg)] + [5 x size (cm)] - (6.75 x age)
♀MB = 655.09 + [9.563 x weight (kg)] + [1.84 x size (cm)] - (4.676 x age)

- Harris-Benedict equations reviewed by Mifflin and St Jeor (1990):

♂ MB = [9.99 x weight (kg)] + [6.25 x height (cm)] - [4.92 x age (years)] + 5
♀MB = [9.99 x weight (kg)] + [6.25 x height (cm)] - [4.92 x age (years)] - 161
Energy Expenditure in Rest

• GER = Basal Metabolism + ADE or ETA (5-10% MB)

Calculation of energy needs

• They can be estimated in three ways:

1. From basal metabolism or resting energy expenditure (GER) and from average factors of physical activity.
2. Based on GER and an individual factor of physical activity.
3. The energy needs can be estimated more accurately using the tables that include the expenditure by physical activity expressed in kcal / kg of weight and time used to carry out the activity.

- Energy expenditure by physical activity, or energy intended for muscle contraction and travel

 From basal metabolism and physical activity factors

• Physical activity factors (Table 1 PDF)

	LIGHT	MODE	HIGH
Men	1.55	1.78	2.10
Female	1.56	1.64	1.82

 Based on GER and an individual factor of physical activity (TABLE 2 PDF)

- Example: woman of 20 years and weight of 60kg
Resting metabolic rate (TMR) = (14.7 x P) + 496
Average physical activity factor (AF) (activity table) = 54 / 24h
Total energy needs = TMR x FA


- Thermal effect of food, or thermogenesis mandatory for the digestive and metabolic use of nutrients.

The first term that was used was that of "specific dynamic action" that referred only to digestive and metabolic processes corresponding to dietary protein.

• It is the third component of energy expenditure, in quantity. • Mandatory thermogenesis is the energy used in the digestion, absorption, distribution, metabolism, excretion and storage of ingested nutrients.
• In a mixed diet, it does not exceed 10% of the total caloric expenditure, being the proteins that carry most of the consumption by induced thermogenesis, compared to intermediate values ​​of carbohydrates and lower lipids.
• Also called "postprandial thermogenesis".
• This energy expenditure fluctuates around 5-10%, although it depends on the macronutrient content of the diet.
• It varies from one individual to another, and in the same individual from one moment to another.

- Optional thermogenesis or energy of adaptation that the body destines to modulate / adjust the energetic balance and that usually it comes off in the form of heat.

• There is also a thermogenesis or heat dissipation, facultative or adaptive that can be induced by various factors (th, drug consumption, psychological state, pathologies), among which is the diet (decrease in intake).
• This process is controlled by the sympathetic nervous system and the decoupling proteins.