Lecture 4 - Fats

Question 1

What makes up a triglyceride molecule?

Answer 1

3 fatty acids + 1 glycerol

Question 2

Key information about triglycerides?

Answer 2

• Largest energy store in the body
• Only macronutrient we can store indefinitely
• Major storage form of fats in the body

Question 3

What reaction forms a triglyceride?

Answer 3

Esterification reaction

- Removal of a water molecule to form a bond, to have fatty acids attached to the glycerol

Question 4

How do we classify different length fatty acids

Answer 4

Carbon chain length
SCFA - <4
MCFA - 6-12
LCFA - >14

Question 5

Difference between long and small chain fatty acids

Answer 5

Longer the chain length the more solid and less liquid the fatty acid becomes at room temperature

Question 6

State the difference between saturated and unsaturated fatty acids

Answer 6

Saturated:
- All carbons have a hydrogen bond
- Stimulate in the liver to form cholesterol (seen as ‘bad’ fat)
Unsaturated:
- There is a double carbon bond replacing a hydrogen bond

Question 7

What are ‘trans fatty acids’?

Answer 7

• Umbrella term for anything modified by high heat and light

- Switching in atomic structure of hydrogen bonds

Question 8

What is the omega number of an essential fatty acid?

Answer 8

• Refers to where the fatty acid becomes unsaturated

- ‘Omega 9’ for example means the double bond (where the fatty acid becomes unsaturated) is 9 carbons from the omega end

Question 9

What does a higher n-3 compared to n-6 produced

Answer 9

Less inflammatory mediators produced

Question 10

Explain about adipose tissue

Answer 10

• Most lipids are stored as adipose tissue
• Generally have more than 8-10KG of adipose tissue
• Not simply a fuel store but also a signalling tissue
• Too much has a negative effect on metabolism

Question 11

Where is the majority of fat oxidised during exercise?

Answer 11

Muscle cells

Question 12

Explain intramuscular triglycerides

Answer 12

• Available in the muscle

- Most immediate energy source with respect to lipids

Question 13

Why are intramuscular triglycerides the most immediate energy source with respect to lipids?

Answer 13

• Lipids are stored in the myofibril spaces - very closed proximity to the mitochondria
• The lipid has to be oxidised in the mitochondria
• Meaning this process can happen quickly
• in obese/type II diabetes patients, these lipids are not available and therefore not used

Question 14

How much energy can we store as fat and CHO

Answer 14

• CHO = 8,000KJ

- Fat = 450, 000KJ

Question 15

Why is it important to tap into fat stores during exercise?

Answer 15

Can delay depletion of carbohydrate stores in the body and therefore exercise for longer

Question 16

Why do both trained and obese individuals have similar amounts of IMTG, but trained individuals use it better?

Answer 16

In trained individuals, the IMTG are located next to the mitochondria, where they are oxidised. In obese individuals, the IMTG is located all over the muscle cell, therefore not easily oxidised

Question 17

How much energy is stored as fat?

Answer 17

415, 000 KJ - 12KG

Question 18

At what point do we start to use more CHO than fat?

Answer 18

65% VO2max

Question 19

Why, at higher intensities do we use more CHO than fat?

Answer 19

CHO is a more efficient fuel due to less oxygen needed, therefore more convenient to use at high intensities

Question 20

Plasma free fatty acid is increased by? Tick all the appropriate answer.
A. Decreased adipose tissue blood flow
B. Increased lipoprotein lipase activity
C. Increase hormone sensitive lipase activity
D. Insulin

Answer 20

B and C

Question 21

Name 2 limitation of fat oxidation during exercise.

Answer 21

Adipose tissue oxidation

Uptake into muscles

Question 22

What can increased fat intake do to glycogen stores?

Answer 22

Increased fat intake generally comes at a cost of CHO, therefore decreased muscle glycogen stores

Question 23

How does depleted IMTG stores effect performance?

Answer 23

Depleted IMTG stores due to low fat decreases performance

Question 24

How does high fat intake effect performance and why?

Answer 24

Generally shown to decrease performance

- Reduced glycogen stores and reduced efficiency of CHO in high intensity exercise

Question 25

What is adrenaline a major activator of?

Answer 25

Hormone sensitive lipase (HSL)

Question 26

What is a normal Fatmax?

Answer 26

55-57%

Question 27

At a fixed workload, would trained or untrained individuals use more fat?

Answer 27

Trained, therefore more glycogen stores for prologued exercise

Question 28

How does exercise duration impact fat oxidation?

Answer 28

Fat oxidation increases with exercise duration

Question 29

At what rate does fat oxidation peak at?

Answer 29

50-65%

Question 30

What metabolic effect does heprin have?

Answer 30

Increases release of lipoprotein lipase - key enzyme for liberating fats for circulating lipoproteins

Question 31

How does consuming CHO before exercise effect fat availability?

Answer 31

Limits FFA availability due to insulin counter regulating adipose tissue lipolysis

Question 32

How does pre exercise fat feeding (+heprin) effect muscle glycogen use?

Answer 32

Consuming a fatty meal with heparin pre exercise increases FFA in the blood and therefore spares glycogen stores

Question 33

Ingesting fat pre exercise with no heparin has what effect on performance?

Answer 33

No effect as the fatty acids are not readily available due to not heprin

Question 34

How does the chain length effect fat oxidation and performance?

Answer 34

No effect

Question 35

How do high fat diets effect performance?

Answer 35

No effect on performance - impairs gluconeogensis and sprint ability

Question 36

Who might you recommend a high fat diet to?

Answer 36

Ultra endurance athletes - they will be simultaneously restoring CHO stores whilst maximising capacity for fat oxidation