6.6. Energy balance of the body. The quantitative and qualitative requirements of food. The regulation of food intake. Control of body weight.

Question 1

I. Energy balance
1. What is energy balance?

Answer 1

Energy balance is the relationship between the energy content of the food consumed and the total amount of energy used by the body.

Question 2

I. Energy balance
2. What are the 3 sources of energy?

Answer 2

carbohydrates, fats and protein

Question 3

I. Energy balance
3. How do we measure the amount of energy?

Answer 3

The amount of energy they provide is measured in calories/joules (1 calorie = 4,2 Joules).
=> Total energy expenditure (TEE) = calorie content of food

Question 4

I. Energy balance
4. Give the amounts of energy content by carbohydrate, fat, protein

Answer 4

• Carbohydrate: 17,2 kJ/g
• Fat: 39 kJ/g
• Protein: 17,2 kJ/g

Question 5

I. Energy balance
5. What is Respiratory quotient (RQ)?

Answer 5

Respiratory quotient (RQ): dimensionless number used in calculations of BMR
- RQ is the ratio of CO2 produced by the body to oxygen consumed by the body

Question 6

I. Energy balance
6. Give the values of RQ by carbohydrate, fat, protein

Answer 6

Question 7

I. Energy balance
7A. What is the Total energy expenditure (TEE)?

Answer 7

• TEE: the net amount of energy used by a living organism to maintain core physiological functions and to allow locomotion (movement)
• TEE = heat formation + external work
• TEE = BMR + DIT (diet-induced thermogenesis) + EE (energy expenditure of work)

Question 8

I. Energy balance
7B. What happen if we have neutral, negative, positive energy balances?

Answer 8

P

Question 9

I. Energy balance
7C. TEE = heat formation + external work
=> What happen if external work = 0

Answer 9

• If external work = 0
  => TEE = heat production

Question 10

I. Energy balance
8A. What are the 2 ways that Total energy expenditure (TEE) can be measured?

Answer 10

1) Direct calorimetry
2) Indirect calorimetry

Question 11

I. Energy balance
8B. How do we measure Total energy expenditure (TEE) by direct calorimetry?

Answer 11

• Measures the amount of heat generated by the body within a room by measuring the amount of melting ice (inconvenient)

Question 12

I. Energy balance
8C. How do we measure Total energy expenditure (TEE) by indirect calorimetry?

Answer 12

• Principle: nearly all energy released in our body is derived from reactions in which oxygen participates (can be seen in the large amounts of ATP produced during oxidative phosphorylation of the ETC)
• 21kJ energy is liberated per 1L of oxygen consumed =>energy equivalent of O2: 21kJ/L
• By measuring O2-consumption during various activities we can estimate energy expenditure

Question 13

I. Energy balance
9A. What is BMR?

Answer 13

BMR is the minimal expenditure required to exist at rest, but at an awake state + w/o any physical activity

Question 14

I. Energy balance
9B. When should we measure BMR?

Answer 14

• Usually measured in the morning
• No physical activity allowed
• Neutral temperature (20 degrees)
• No food 12h prior to measurement
• No external stimuli allowed (stress/emotions)
• No drugs (medication)

Question 15

I. Energy balance
9C. What are normal BMR values in men and women?

Answer 15

• Men: 7000 kJ/day
• Women: 6000 kJ/day

Question 16

I. Energy balance
9D1. What are the 8 factors that influence BMR?

Answer 16

Question 17

I. Energy balance - factors influence BMR
9D2. One of the 8 factors that influence BMR is
“BODY SIZE”
=> Explain why

Answer 17

BMR increases as weight, height and surface area increase

Question 18

I. Energy balance - factors influence BMR
9D3. One of the 8 factors that influence BMR is
“SEX”
=> Explain why

Answer 18

BMR usually lower in women due to more body fat + less muscle

Question 19

I. Energy balance - factors influence BMR
9D4. One of the 8 factors that influence BMR is
“AGE”
=> Explain why

Answer 19

BMR declines with age

Question 20

I. Energy balance - factors influence BMR
9D5. One of the 8 factors that influence BMR is
“CLIMATE”
=> Explain why

Answer 20

BMR is higher in tropical climates, because cooling of body takes energy

Question 21

I. Energy balance - factors influence BMR
9D6. One of the 8 factors that influence BMR is
“Body temperature”
=> Explain why

Answer 21

BMR is higher with fever

Question 22

I. Energy balance - factors influence BMR
9D7. One of the 8 factors that influence BMR is
“T3/T4, catecholamines”
=> Explain why

Answer 22

BMR is increased

Question 23

I. Energy balance
10. What are the features of Diet-induced thermogenesis (DIT)?

Answer 23

Food intake -> heat production↑ (GI-motility, hormonal effects)
=> ~ 15 – 30% of TEE

Question 24

I. Energy balance
11. What are the features of Energy expenditure (EE) of physical activity?

Answer 24

Dependent on lifestyle, occupation etc.
=> ~ 15 – 20% of TEE

Question 25

II. Quality requirement of food
1. What is the Quality requirement of food?

Answer 25

Calorie content has to cover TEE
- Rule of isodynamics: different nutrients can replace each other in energy-equivalent amounts
- Restrictions: essential AAs, essential fatty acids, GI physiology (different mechanisms of GI-tract require a balanced diet)

Question 26

II. Quality requirement of food
2. What is the Rule of isodynamics?

Answer 26

Different nutrients can replace each other in energy-equivalent amounts

Question 27

II. Quality requirement of food
3. What are the Restrictions?

Answer 27

• Restrictions: essential AAs, essential fatty acids, GI physiology (different mechanisms of GI-tract require a balanced diet)

Question 28

III. Heat production
1. What is Heat production?

Answer 28

Heat production is usually just a side effect of the metabolic processes of our body, but some tissues are specialized for heat production such as Brown adipose tissue and Beige adipose tissue

Question 29

III. Heat production
2A. What are the features of Brown adipose tissue?

Answer 29

• Rich in mitochondria (gives its brown appearance + thermogenic function) and contains less fat
• Not usually present in adult human (only small amount)
• Uncoupling protein 1 (UCP1) found in mitochondria:

Question 30

III. Heat production
2B. What is the mechanism of Uncoupling protein 1 (UCP1) in brow adipose tissue?

Answer 30

A TM protein that allows protons to flow from the intermembrane space to the matrix, thus, decreasing the proton gradient necessary for ATP synthase to phosphorylate ADP
=> allowing heat production

Question 31

III. Heat production
3A. What are the features of Beige adipose tissue?

Answer 31

• Found in adult humans
• Contains mitochondria with UPC1 = able to carry out thermogenesis
• Exposure to cold temperature and presence of catecholamines (NE + E) stimulate cell differentiation to beige adipose tissue, which leads to more heat production

Question 32

III. Heat production
4. Make a schematic diagram of generation of white and beige adipocytes

Answer 32

Question 33

IV. Regulation of food intake. Control of body weight
1. Which part of the brain participate in Regulation of food intake?

Answer 33

Specialized areas of the HT analyze incoming afferent signals, and through various efferent pathways they coordinate food-seeking and thermogenesis to maintain appropriate long- term and short-term energy needs.
- A satiety center
- The arcuate nucleus

Question 34

IV. Regulation of food intake. Control of body weight
2. What are the features of satiety center?

Answer 34

A satiety center inhibits appetite even in the presence of food, and there is also a feeding center with the opposite effect. Information feeds into these two centers from the arcuate nucleus.

Question 35

IV. Regulation of food intake. Control of body weight
3. What are the features of the arcuate nucleus?

Answer 35

• The arcuate nucleus has various neurons that project onto the satiety feeding centers, these being anorexigenic and orexigenic neurons.
• Anorexigenic neurons release POMC which leads to decreased appetite, and orexigenic neurons release neuropeptide Y to cause increased appetite.

Question 36

IV. Regulation of food intake. Control of body weight
4. What are the 3 Factors that act on the arcuate nucleus => influence hunger and feeding?

Answer 36

• Leptin
• Insulin
• Neuropeptides

Question 37

IV. Regulation of food intake. Control of body weight
5. How does leptin act on the arcuate nucleus that influence hunger and feeding?

Answer 37

Leptin: ↑secretion when adipose tissue mass expands
=> leptin decreases hunger by
stimulating anorexigenic neurons + increasing thermogenesis + energy expenditure

Question 38

IV. Regulation of food intake. Control of body weight
6. How does insulin act on the arcuate nucleus that influence hunger and feeding?

Answer 38

reinforces the above process by stimulating anorexigenic neurons / inhibiting orexigenic neurons

Question 39

IV. Regulation of food intake. Control of body weight
7A. How does Neuropeptides act on the arcuate nucleus that influence hunger and feeding?

Answer 39

Neuropeptides: hormones from the GI-system respond to presence/absence of food
by signaling the HT:
- Hunger decreased by: GLP-1, CCK, CART (cocaine-and-amphetamine regulated transcript)
- Hunger increased by: Ghrelin, orexins (stimulate hunger + awakeness, help fight against sleep)

Question 40

IV. Regulation of food intake. Control of body weight
7B. Which neuropeptides that decrease hunger?

Answer 40

Neuropeptides: hormones from the GI-system respond to presence/absence of food
by signaling the HT:
- Hunger decreased by: GLP-1, CCK, CART (cocaine-and-amphetamine regulated transcript)

Question 41

IV. Regulation of food intake. Control of body weight
7C. Which neuropeptides that increase hunger?

Answer 41

Neuropeptides: hormones from the GI-system respond to presence/absence of food by signaling the HT:
- Hunger increased by: Ghrelin, orexins (stimulate hunger + awakeness, help fight against sleep)

Question 42

IV. Regulation of food intake. Control of body weight
8. Make a schematic diagram of Regulation of food intake

Answer 42