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Calculation of daily caloric needs scientifically known as Total Daily Energy Expenditure (GET) and Difference between Indirect Calorimetry and the Harris-Benedict Formula.

1. Indirect Calorimetry to Calculate Basal Energy Expenditure (GEB) or at rest Indirect calorimetry measures basal energy expenditure (GEB) directly through oxygen consumption (VO₂) and carbon dioxide production (VCO₂). Basal metabolic rate affects the rate at which a person burns calories and, ultimately, whether that person maintains, gains, or loses weight. The basal metabolic rate represents around 60 to 75% of individuals' daily caloric expenditure. It is influenced by several factors. It generally decreases by 1 to 2% per decade after age 20, mainly due to loss of muscle mass although variability between individuals is high.

How to perform it: 1. Measurement under conditions of fasting or low intake and complete rest. 2. Obtaining VO₂ and VCO₂ values. 3. Application of the formula to calculate the GEB.

2. Calculation of daily caloric needs using the Harris-Benedict Formula. It uses anthropometric data, such as weight, height, sex, and demographics to estimate GEB. Key Differences: • Indirect Calorimetry: Measures the GEB directly and specifically for each individual, providing a more precise estimate, where metabolism, muscle mass, your hormonal situation, and your nervous system are measured, through the analysis of the exchange of respiratory gases, heart rate and respiratory rate. • Harris-Benedict: Estimates the GEB based on population averages, which may not reflect the high and significant individual variations.

3. Physical Activity Factor (NAF) Another factor to take into account is the NAF, adjusts the GEB according to the individual's level of physical activity. It is assigned according to Categories and Factors:

1. Sedentary (NAF = 1.2): Little or no exercise.

2. Light activity (NAF = 1.375): Light exercise or sport 1-3 days a week.

3. Moderately active (NAF = 1.55): Moderate exercise or sport 3-5 days a week. 4. Very active (NAF = 1.725): Intense exercise or sport 6-7 days a week.

5. Super active (NAF = 1.9): Very intense exercise or strenuous physical work.

4. Food Thermogenesis (TEF) TEF is the energy used to digest and metabolize food, representing approximately 10% of total energy expenditure.

Factors Affecting Food Thermogenesis

1. Diet composition:

• Proteins: They generate the greatest thermic effect, increasing energy expenditure by 15-30% of the caloric content of the ingested proteins.

• Carbohydrates: They generate a thermic effect of 5-10%.

• Fats: They generate the lowest thermal effect, 0-3%.

2. Amount of food: A greater amount of food consumed tends to increase the thermic effect.

3. Meal frequency: Eating several times a day in small quantities can have a different impact compared to eating a few times in large quantities.

4. Health status and age: Age and certain medical conditions can alter the metabolic response to food.

Importance of Food Thermogenesis

TEF is an important consideration in body weight regulation and energy management. A higher TEF may contribute to higher total energy expenditure, facilitating weight maintenance or weight loss.

On the other hand, low protein diets may have a lower TEF, reducing energy expenditure.

In Conclusion Food thermogenesis is a vital component of total energy expenditure, influenced by the composition and quantity of food ingested, as well as individual factors such as age and health. Understanding how different macronutrients affect TEF may be useful in dietary planning for weight management and optimization of metabolic performance. It is estimated globally, multiplying the basal metabolic rate and the physical activity factor by 1.1.

Then, summarizing the Calculation of Energy Expenditure Adjusted for Physical Activity, we obtain: by multiplying the metabolic rate at rest obtained by indirect calorimetry, by the physical activity factor of that person (NAF) and by the thermogenesis of food, that is, 1 ,1.


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