Energy Needs

Question 1

1. What 5 factors affect energy intake?

Answer 1

• Hunger
• Desire to eat
• Social influences
• Emotional factors
• Learned preferences and aversion

Question 2

2. What 6 factors affect energy expenditure (EE)?

Answer 2

• Body size
• Body mass + weight + height (BMI)
• Body composition (fat-free mass is the strongest determinant)
• Age
• Gender
• Diseases (genetics)

Question 3

3. What does energy output determine and what is it derived from (sources of energy output)?

Answer 3

• Determines energy expenditure

- Derived from basal metabolism (BMR), physical activity, thermogenesis, growth, pregnancy & lactation

Question 4

4. Define basal metabolic rate (BMR) and give the conditions it is measured under.

Answer 4

• Minimum energy it takes to keep a resting awake body alive
• Conditions: Emotionally relaxed, 12 hours fasted, no previous strenuous exercise, lying supine, completely still, after waking in the morning, healthy, thermoneutral environment.

Question 5

5. What factors/processes does BMR involve?

Answer 5

• Cell function & replacement
• Synthesis, secretion and metabolism of enzymes, hormones, other substances
• Maintenance of body temperature
• Cardiac and respiratory muscle function
• Brain function, breathing, heart pumping

Question 6

6. What percentage of daily energy expenditure is the BMR?

Answer 6

45-70%

Question 7

7. What is BMR determined by?

Answer 7

• Body mass
• Fat free mass (strongest determinant)
• Gender
• Age
• Height
• Body composition
• Genetic variation

Question 8

8. State the two methods of measuring BMR and what they measure.

Answer 8

• Direct calorimetry: measures heat loss (direct measurement of energy that has been used)
• Indirect calorimetry: measures heat production by assessing O2 consumption and CO2 production

Question 9

9. What is Lavoiser’s calorimeter?

Answer 9

• Example of direct calorimetry
• Ice cavity surrounded by a space with snow (to maintain temperature) and a guinea pig is placed in the cavity. Heat from the animal causes the ice to melt in the inner jacket and this is collected and weighed.

Question 10

10. State the disadvantages of direct calorimetry.

Answer 10

• Expensive, time-consuming and limited application for human studies

Question 11

11. Define a whole body calorimeter/respiration chamber.

Answer 11

• Room where a person stays for a set period of time, the heat loss is measured, for overall EE, every 24 hours and this is used for physiological experiments

Question 12

12. Explain the concept of indirect calorimetry.

Answer 12

• There is a relationship between O2 consumed and the amount of heat produced by the body, providing an estimate of the metabolic rate. But measure of O2 consumption is indirect since heat is not measured directly.