Energy requirement calculation ***

Question 1

What are the key elements of the Total Energy Expenditure (TEE) in healthy subjects?

Answer 1

• Resting Energy Expenditure (REE): About 60% of TEE.
• Activity induced Energy Expenditure (AEE): About 30% of TEE.
• Diet induced Energy Expenditure (DIT or TEF): About 10% of TEE.

Question 2

What is the primary component of total energy expenditure comprising 60–70%?

Answer 2

Basal Metabolic Rate (BMR).

Question 3

What is a product of mainly the metabolism of lean body mass and is therefore dependent on variables related to it, such as body weight, height, sex, and age?

Answer 3

Resting Energy Expenditure (REE) or Basal Energy Expenditure (BEE).

Question 4

What is the energy required to thermoregulate and respond to changes in the environmental temperature, that comprises 10–15% of total energy expenditure?

Answer 4

Adaptive thermogenesis.

Question 5

What percentage of the TEE is comprised by the diet induced thermogenesis (DIT)?

Answer 5

10–15%

Question 6

What is the most variable component of total energy expenditure, and accounts for 15- 50% of TEE?

Answer 6

Activity induced energy expenditure.

Question 7

What is considered the gold standard to measure caloric needs?

Answer 7

The calculation of heat production from chemical processes.

Question 8

Which type of calorimetry involves measuring energy expenditure through the measurement of the production or loss of heat by the use of a ventilation hood and a respiration chamber to continuously measure VO2 and VCO2?

Answer 8

Direct calorimetry.

Question 9

Which type of calorimetry involves the measurement of heat production by measuring O2 consumption and/or production of CO2 (both in mL/min)?

Answer 9

Indirect calorimetry.

Question 10

What is the respiratory quotient used for?

Answer 10

To evaluate substrate utilization.

Question 11

What are the different parameters of the respiratory quotient?

Answer 11

• For fat metabolism, the RQ is around 0.7
• For carbohydrate metabolism, the RQ is around 0.95-1.0
• For a mixed diet, the RQ is around 0.85
• A respiratory quotient of 1.0 may indicate excessive CO2, lipogenesis, and overfeeding.

An RQ above 1 is not physiologically possible and likely indicates technical issues with the measurement. An RQ below 0.6 may indicate ketosis.

Question 12

What are the most famous prediction equations for the calculation of TEE?

Answer 12

The Harris-Benedict, Ireton-Jones and Mifflin-St Jeor formulas.

Question 13

When is the rule-of-thumb used for the calculation of TEE?

Answer 13

If the usage of indirect calorimetry is impossible, or the use of predictive equation is not feasible.

Question 14

What is the rule-of-thumb?

Answer 14

• 20-25 kcal/kg of weight for overweight patients.
• 30 kcal/kg of weight for patients with normal weight.

Question 15

What components are the principal source of energy in a normal diet (particularly during anaerobic exercise), and comprise 40–55% of energy requirements in the Western diet?

Answer 15

Carbohydrates

Question 16

What components represent the major form of energy storage in the body, with high content of energy and low hydration?

Answer 16

Dietary lipids.

Question 17

How much energy do dietary lipids contain?

Answer 17

1 g of triglyceride carries 9.3 kcal.

Question 18

What are the three types of dietary fatty acids?

Answer 18

• Saturated
• Monounsaturated
• Polyunsaturated

Question 19

What are the three types of aminoacids?

Answer 19

• Non-essential amino acids.
• Conditionally essential amino acids.
• Essential amino acids.

Question 20

What is an example of a conditionally essential amino acid?

Answer 20

Glutamine, which may become essential in certain disease states if the requirement for particular amino acids is increased.

Question 21

What are the recommendations for carbs, fat and protein regarding their involvement in the TEE?

Answer 21

• Carbs (CHOs): 40-55% of total energy, 50% of TEE, less than 10% from sugar.
• Fat: 25-35% of total energy, 30% of TEE, less than 10% from saturated fatty acids.
• Protein: 15-20% of the total energy, 20% of TEE.

Question 22

What’s the energy content of carbs, protein and fat?

Answer 22

• 1 g carb = 4 kcal
• 1 g prot = 4 kcal
• 1 g fat = 9 kcal

Question 23

What are the four methods of calculating the energy requirements?

Answer 23

• Direct calorimetry.
• Indirect calorimetry.
• Prediction equations.
• Rule of thumb.

Question 24

What is the Harris-Benedict equation for men?

Answer 24

BMR = 88.362 + (13.397 ⨯ weight in kg) + (4.799 ⨯ height in cm) - (5.677 ⨯ age in years)

Question 25

What is the Harris-Benedict equation for women?

Answer 25

BMR = 447.593 + (9.247 ⨯ weight in kg) + (3.098 ⨯ height in cm) - (4.330 ⨯ age in years)

Question 26

Which prediction equation created in the 1990s provided a valid estimate of RMR?

Answer 26

The Mifflin-St Jeor formula.

Question 27

Which prediction equation revised by Roza and Shizigal in 1984 provided a valid estimate of BMR?

Answer 27

The Harris-Benedict equiation.

Question 28

What is the Mifflin-St Jeor formula for men?

Answer 28

RMR = (10 ⨯ weight in kg) + (6.25 ⨯ height in cm) - (5 ⨯ age in years) + 5

Question 29

What is the Mifflin-St Jeor formula for women?

Answer 29

RMR = (10 ⨯ weight in kg) + (6.25 ⨯ height in cm) - (5 ⨯ age in years) - 161

Question 30

What are the limitations of Indirect calorimetry?

Answer 30

• Poor equipment
• Unskilled personnel doing the test
• Lack of ability to interpret the data
• Challenges in ICU situations with ventilators, oxygen sources and compliant patient

Question 31

What is the meaning of a respiratory quotient more than 1 in an indirect calorimetry?

Answer 31

If the respiratory quotient measured by indirect calorimetry is above 1, it likely
indicates hyperventilation and the test will not be accurate. An RQ above 1 is not
physiologically possible since it would require more carbon dioxide to be
produced than oxygen consumed. Therefore, if an RQ above 1 is measured, it is
likely due to technical issues with the measurement rather than a true metabolic
phenomenon.

Question 32

What is the relation between indirect calorimetry and the predictive equations for calculating the resting metabolic rate?

Answer 32

Predictive equations developed for normal healthy subjects may not be accurate
for critically ill patients due to various factors that can affect resting metabolic
rate. Indirect calorimetry, on the other hand, can measure resting metabolic rate
under standard conditions to obtain a steady state resting metabolic rate, making
it a more reliable method for measuring resting metabolic rate compared to
predictive equations.

Question 33

What are the pros of indirect calorimetry?

Answer 33

• Can provide information on substrate utilization and energy expenditure.
• Can be used to monitor changes in energy expenditure over time.
• Can measure resting metabolic rate under standard conditions to obtain a steady state RMR.

Question 34

What are the pros of Predictive equation?

Answer 34

• Can be easily calculated using simple equations.
• Can provide a rough estimate of resting metabolic rate.
• Can be used in situations where indirect calorimetry is not available or feasible.