Energy balance and substrate metabolism Flashcards

1
Q

How can energy balance be altered?

A

Changing energy intake or expenditure

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2
Q

Positive energy balance?

A

More in than out

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3
Q

Negative energy balance?

A

More out than in

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4
Q

How to increase energy balance?

A

Increase intake/decrease expenditure

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5
Q

How to decrease energy balance?

A

Decrease intake/increase expenditure

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6
Q

What components of energy intake are there?

A

Carbs, fat, protein, alcohol

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7
Q

Components of energy expenditure?

A

Resting metabolic rate (RMR), dietary induced thermogenesis (DIT), Physical activity energy expenditure (PAEE)

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8
Q

What is RMR?

A

Resting metabolic rate–> the energy needed to keep us alive

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9
Q

What is DIT?

A

Energy used to digest, absorb and metabolise the food we have eaten

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10
Q

What is PAEE?

A

Energy used by muscles when they produce force

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11
Q

Two main energy stores?

A

Carbs and fat

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12
Q

Which energy store can store more energy (fat or carbs)?

A

Fat

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13
Q

Where can fat be stored?

A

Blood, muscle and adipose tissue

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14
Q

Where is the largest method of storing fat?

A

Adipose tissue

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15
Q

How much fat (in kcal) can be stored?

A

> 100,000

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16
Q

Where can carbohydrates be stored?

A

Blood, muscle, liver

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17
Q

Where is the largest carbohydrate store?

A

Muscles

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18
Q

In what form is the largest carbohydrate store kept?

A

Glycogen

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19
Q

What is the relationship between endurance training status and amount of muscle glycogen that someone can store?

A

More endurance trained means ability to store more muscle glycogen

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20
Q

How much carbs can the body store?

A

3200 kcal

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21
Q

What is denovolipogenesis?

A

Conversion of non-fat sources to fat

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22
Q

What happens if you have more than 3200kcal of carbs?

A

Denovolipogenesis

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23
Q

What is leptin?

A

A hormone

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24
Q

Role of leptin?

A

Regulates appetite

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25
Q

What is the result of someone with leptin deficiency?

A

They gain a lot of non-lean body mass

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26
Q

What kind of tissue releases leptin?

A

Fat tissue

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27
Q

What happens to leptin secretion as a result of an increase in fat?

A

The fat tissue releases more leptin

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28
Q

Cause of leptin deficiency?

A

Mutation in gene sequence coding for the leptin protein

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29
Q

Main issue with measuring energy intake?

A

Observation effect–> when you know someone is observing you you modify your behaviour,
reporting bias–>sometimes people underreport what they consume,
participant recall–> people forget what theyve eaten

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30
Q

Which kind of sports have the highest energy intake?

A

Endurance (cross country skiing, triathlon) and large muscle mass (rugby, bodybuilding)

31
Q

What is the energy density of protein?

A

4kcal/g

32
Q

What is the energy density of fat?

A

9kcal/g

33
Q

What is the energy density of carbohydrates?

A

4kcal/g

34
Q

What is the energy density of ethanol?

A

7kcal/g

35
Q

Difference in energy balance in high or low fat diet?

A

High fat diet leads to more fat balance (high +ve) than low fat diet (-ve) , difference is >400g

36
Q

What is the difference in calories consumed between high and low fat diets (mass of food consumed is same)?

A

High fat diets have a higher energy intake than low fat diets as fats are more energy dense than carbs

37
Q

What is most of the difference in energy balance between high and low fat diets caused by?

A

Energy density

38
Q

Which macronutrient is the most satiating?

A

Protein

39
Q

What is a preload drink?

A

A drink drunk before a large intake of energy (a meal)

40
Q

What happens to energy intake of a meal as the protein content of the preload drunk before increases?

A

It decreases

41
Q

What is measured in direct calorimetry?

A

The heat produced by someone

42
Q

Issues with a direct calorimetry machine?

A

Need to be quite small (people cant move), very expensive

43
Q

What does indirect calorimetry measure?

A

Oxygen consumption and carbon dioxide production

44
Q

Ways to measure energy expenditure in free living conditionds?

A

Self report questionnaire, doubly labelled water, pedometers, accelerometers, accelerometry and heart rate combined (aciheart)

45
Q

Benefits of self report energy expenditure?

A

Easy to administer to a large group, low cost

46
Q

Issues of self report energy expenditure?

A

Reporting bias–> underreport intake and overreport exercise

47
Q

Benefits of doubly labelled water?

A

Precise and accurate

48
Q

Issues with doubly labelled water?

A

Expensive and technically challenging-> cannot be used on a large group

49
Q

What does the AciHeart measure?

A

Accelerometry and heart rate

50
Q

How does doubly labelled water work?

A

Ingest a dose of water with heavier H and O isotopes. O loss is steeper when measured as it is lost in CO2 and H20 whereas H is only lost in H2O. Difference between the two is the average CO2 produced over that time period

51
Q

Strengths of DLW?

A

Doesnt need to rely on accurate patient reporting

52
Q

Technical limitations of DLW?

A

Ratio of CO2 production to O2 consumption varied depending on diet of person, so O2 consumption isnt an exact measure it is inferred

53
Q

Issue with using DLW at high exercise intensities?

A

High exercise intensity results in acidosis (H+ production) which is buffered by bicarbonate system–> produces CO2 from non-metabolic processes

54
Q

Fuel source issue w/ DLW?

A

Can be oxidising things like lactate, ketone bodies, protein as well as Carbs and Fat

55
Q

Tissue specific measurement of substrate metabolism method?

A

Tracer based–> infuse a labeled form of glucose into a vein, ingest another form of carb–> measure exogenous carb oxidation

56
Q

What can be measured from tissue specific measurement of substrate metabolism?

A

Exogenous carb production

57
Q

Link between exercise intensity and fuel consumption?

A

At higher intensity exercises, carbohydrate fuels are used more than fats

58
Q

Effect of duration of exercise on fuel consumption?

A

Decrease in carb use and an increase in fat use

59
Q

Which metabolic fuels are blood based?

A

Plasma glucose, circulating FFA

60
Q

Contribution of muscle based fuels as exercise duration increases?

A

Decreases

61
Q

Why does the contribution of muscle based fuels decrease as exercise duration increases?

A

Muscle fuels are depleted over the course of exercise so the longer it goes on the less readily available they are

62
Q

What effect on fuel use does ingesting Cho have?

A

Decrease fat oxidation and increase carb oxidation

63
Q

Which sex has the greater capacity for fat oxidation?

A

Women

64
Q

Effect of VO2max on muscle glycogen storage?

A

Increases it

65
Q

Effect of a high carb diet on glycogen storage capacity?

A

Increases it

66
Q

What effect does a higher glycogen conc pre exercise have on glycogenolysis?

A

More glycogen at start of exercise = more glycogen is used

67
Q

What must be done to the triacyl glycerides in fat before they can be used as a fuel by muscle?

A

Hydrolysed

68
Q

Product of hydrolysis of triacylglycerides?

A

Glycerol and FAs

69
Q

Which transport protein allows FAs to get into muscle mitochondria?

A

CPT1

70
Q

Which enzyme hydrolyses VLDLs and chylomicrons?

A

Lipoprotein lipase (LPL)

71
Q

What could limit NEFA availability?

A

Adipose tissue blood flow

72
Q

Transarcolemal meaning?

A

Transport across the muscle membrane

73
Q

What limits fat oxidation at high exercise intensities?

A

Transport into mitochondria