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HUNT245 > Lecture 2b: Fat Metabolism > Flashcards

Lecture 2b: Fat Metabolism Flashcards

1
Q

What lipids are transported directly into blood?

A
  1. Glycerol
  2. Short-chain fatty acids
  3. Medium-chain fatty acids
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2
Q

What lipids are transported through lymph system and then blood?

A
  1. Triglycerides
  2. Cholesterol
  3. Phospholipids
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3
Q

What is the historical overview of fat and CHO usage?

A

In the 1900’s high fat diets were promoted, then came fat and CHO diets in the 1910’s and by 1960s CHO popularity grew

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4
Q

High CHO diet increases the stores of what?

A

Increases muscle glycogen stores

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5
Q

What does increased muscle glycogen stores do for endurance capacity?

A

Delays onset of fatigue and therefore increases endurance capacity

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6
Q

Trained vs Untrained fat usage during exercise

A

A trained person will use more fat than an untrained person at a given intensity

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7
Q

High fat diet: Metabolic adaption to capillarisation

A

Increased capillarisation of muscle (Increased blood flow)

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8
Q

High fat diet: Metabolic adaption to TAG

A

Increased Intramuscular Triglycerides (IMTG) content

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9
Q

High fat diet: Metabolic adaption to sensitivity

A

Increased sensitivity of adipose & muscle cells to epinephrine

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10
Q

High fat diet: Metabolic adaption to mitochondria

A

Increase in number & size of skeletal muscle mitochondria

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11
Q

High fat diet: Metabolic adaption to enzymes

A
  • Increase in enzymes involved in fat transport and metabolism
  • Increased activity of oxidative enzymes
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12
Q

What do all the metabolic adaptions to exercise from high fat diets lead to?

A

increased use of fat as a fuel

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13
Q

What is the adaption to endurance exercise?

A

Metabolic adaptations to endurance exercise allow a trained individual to use proportionally more fat and less CHO at a given workload.

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14
Q

What is the adaption to high fat diets?

A

Some research has shown that people adapted to high fat diets undergo similar metabolic changes as those seen with endurance training e.g. Increased intra-muscular TG, changes in enzymes involved in fat oxidation e.g. carnitine palmitoyl transferase.

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15
Q

What is one potential limitation of high CHO diets?

A

CHO oxidation is increased, reducing fat oxidation

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16
Q

Increasing the proportion of fat used during exercise will increase what?

A

the rate of CHO utilisation - spare muscle glycogen. Optimising fat usage means you can conserve the CHO store for when intensity is high.

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17
Q

Why do we want to savour CHO stores?

A

Unlike CHO there is virtually unlimited storage of fat

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18
Q

Why is fat the easiest way to increase energy intake?

A

It is energy dense:
Per gram of fat = 37kJ
Per gram of CHO = 17kJ

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19
Q

How much ATP does fat produce per gram?

A

147ATP

20
Q

How much ATP does CHO produce per gram?

A

38ATP

21
Q

How much storage of fat does the body have?

A

5500 - 10500 g

22
Q

How much storage of CHO does the body have?

A

620 - 650 g

23
Q

Disadvantage of fat as a fuel - oxygen

A

CHO produces greater ATP yield per unit of oxygen

24
Q

Disadvantage of fat as a fuel - transportation in blood

A

Fat = via lymph system
CHO = intestinal abosrbtion

25
Q

Disadvantage of fat as a fuel - intensity

A

Cannot be used anaerobically - need oxygen

26
Q

What are the main storage sites of fat?

A

As triglycerides in Adipose tissue (5000-10000g)
As intra-muscular triglyceride in muscle (350g)

27
Q

What are the main storage sites of CHO?

A

As glycogen in Muscle (500g)
As glycogen in Liver (100-120g)
As glucose in blood plasma (25g)

28
Q

What happens to fat when you just start exercising?

A

TAG’s are broken into FFA and glycerol. Glycerol goes to the liver and FFA’s are transported to muscle

29
Q

What happens once FFA’s reach muscle cells?

A

Enter the mitochondria to generate ATP

30
Q

What effects the rate of fat oxidation?

A
  • Exercise intensity
  • Exercise duration
  • Preceding diet
  • Training status
  • Plasma FFA (Free Fatty Acids) concentration
  • Endogenous and exogenous CHO availability
31
Q

At rest, what percentage of energy comes from fat?

A

over 50%

32
Q

At 25% VO2 max, what percentage of energy comes from fat?

A

over 80% (fat dominant)

33
Q

At 65% VO2 max what percent of energy comes from fat?

A

50% fat, increased IMTG use

34
Q

At 85% VO2 max, what percent of energy comes from fat?

A

25% fat, decreased plasma FFA, decreased IMTG use

35
Q

What is the short term adaption to high fat diets? (1-3 days)

A

Decreased resting muscle & liver glycogen stores.
Decreased CHO oxidation during subsequent exercise.
Impairment of endurance capacity & performance of prolonged exercise.

36
Q

What are the short term adaptions to high fat diets (5-10 days)?

A
  • Metabolic adaptations -> increased fat oxidation during exercise
  • Compensate for decreased CHO availability
37
Q

How long does it take for training capacity to be restored on a ketogenic/high fat diet?

A

within 2-3 weeks, but very variable between athletes

38
Q

What does fat oxidation look like after 3 weeks on a ketogenic diet?

A
  • Maximal rates of fat oxidation shift from 45% to 70% VO2peak
  • Overall fat oxidation rates increase
39
Q

What is the general consensus of performance on a ketogenic diet?

A

No difference or worse off

40
Q

High fat vs High CHO diet for endurance performance

A

Majority of studies show no difference

41
Q

What diet do sports nutritionists recommend?

A

do not recommend a “high carbohydrate diet’ for all athletes, an individualised approach

42
Q

How should CHO intake be periodised?

A

should not be static, but periodised across training cycles according to the fuel cost of training load, and importance of training

43
Q

When should there be high CHO availability?

A

high intensity /volume /quality / technique

44
Q

What factors do we need to consider when designing diets? (Individual)

A

Individual preference: High fat diets = psychological impact

45
Q

What factors do we need to consider when designing diets? (energy)

A

Total energy expenditure: Many sporting events require athletes to exercise for many hours over
several days or weeks

46
Q

What factors do we need to consider when designing diets? (recovery)

A

Limited time for recovery could mean limited time for glycogen repletion

47
Q

What should you conduct a meal plan and nutrition principles based on?

A
  • Meeting energy expenditure
  • Minimising weight loss
  • Optimise Energy : weight ratio of foods
  • Nature of event
  • Preference

HUNT245 (14 decks)

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