WEEK 4 Energy expenditure and physical activity Flashcards

1
Q

What is direct vs indirect calorimetry?

A

Measuring energy expenditure based on heat release = direct calorimetry, to distinguish it from measurements based on gas exchange = indirect calorimetry.

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2
Q

What is the procedure of DLW and what is measured?

A
  1. Stable isotopes (2H2O: deuterium and Oxygen-18: 18O) are ingested as water.
  2. Distributed in the body water pool
    3a. Deuterium = eliminated as water
    3b. Oxygen isotope = eliminated as water + CO2

Difference in elimination rate = CO2 production over the measurement time.

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3
Q

Formula for energy expenditure?

A

Food + O2 -> H2O + CO2 + energy (heat+work)

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4
Q

What is the principle of direct calorimetry?

A

If external work = 0, the heat energy delivered from the chamber = equal to metabolic rate.
Very accurate, but not convenient at all

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5
Q

What is the principle of indirect calorimetry? What is it dependent on?

A

Released energy from substrates is related to O2 consumption (VO2) and CO2 production (VO2). Computes heat from gaseous exchange
(However, depends on the substrate. Meal/diet = mix different substrates)

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6
Q

What are two disadv. of calorimetry?

A
  • Specialized (expensive) equipment
  • Only applicable in lab settings, limited in free-living conditions
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7
Q

DLW: when are the two samples collected? ‘formula’ of elimination and production?

A

Collect two measurement: initial sample (equilibrium) and between 4 - 24 days

18O elimination (water+CO2) - 2H2 elimination (water) = CO2 production (VCO2)

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8
Q

Pro’s of DLW?

A
  • Considered golden standard
  • Validity has been established in respiration chamber
  • Free living
  • Measurement error <5%
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9
Q

Cons of DLW?

A
  • High cost, specialized equipment, labour intensive
  • TEE over 4-21 days: no information other components (PA)
  • small sample size
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10
Q

Assumptions for DLW?

A

> Total body water remains constant (no weight loss)

> No isotopic exchange with non-aqueous body tissue (correct for that) and fractionation (correction factors)

> RER (RQ) 0> 0.85 on mixed diet
(respiratory quotient)

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11
Q

What is something to take into mind with heart rate monitoring?

A

> Low heart rate correlation to EE with low exercise (also, stress, caffeine, ill etc)

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12
Q

T(D)EE =?

A

Total (daily) energy expenditure

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13
Q

What are the 3 components of TEE? %?

A
  1. BMR (basal metabolic rate) ~60-70%
  2. DIT (Diet-induced thermogenesis) ~10%
  3. PA (Physical activity) ~20-30%
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14
Q

BMR = not the same as resting (RMR) or sleeping (SMR) metabolic rate. What is it dependent on?

A
  • Body weight and body composition
  • Age & sex
  • Various (climate, life cycle, external factors)
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15
Q

BMR = not the same as resting (RMR) or sleeping (SMR) metabolic rate. What is it dependent on?

A
  • Body weight and body composition
  • Age & sex
  • Various (climate, life cycle, external factors)
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16
Q

What does DIT depend on?

A
  • size of meal
  • composition of meal
  • texture of meal
  • non-nutrient substances
17
Q

Physical activity can be measured in MET scores. 1 MET = ?

A

1 MET = basal (resting) metabolic state

18
Q

PAL = ? formula?

A

Physical activity level. PAL = TEE/BMR

19
Q

Difference MET and PAL?

A

MET is more for specific excercises, PAL more general for daily activity

20
Q

What is the cutoff of METs for PA do be sedentary?

21
Q

Categorize PAL values from bed rest to very high activity level

A

< 1.2 = Bed rested
1.2 - 1.55 = Low activity level: sedentary
1.55 - 1.71 = Medium activity level, office work
1.71 - 1.95 = high activity level, manual work and exercise
> 1.95 = Very high activity level: Fair amount of manual work or exercise training

22
Q

What is the formula of PAL?

A

PAL = TEE/RMR(or BMR)

23
Q

What is the formula of TEE?

A

TEE = PAEE + RMR(or BMR) + DIT

24
Q

What is the formula of DIT?

A

DIT = 10% of TEE

25
What is the most variable part of TEE?
PA level
26
What are the 4 methods to assess PA/EE?
* Indirect calorimetry & doubly labelled water * Self reported methods - Questionnaire - Logs/diaries * Heart rate monitor * Motion sensors - Pedometer - Accelerometers
27
Cons of indirect calorimetry?
Costly, labour intensive, specialized equipment Restricted to small sample size Non-free living
28
Pros of self-reported methods?
- Low costs - Large population - Costumisable (choose time frame/specific exercise) - Easy
29
Cons self-reported measures?
- Poor correlation with EE (DLW) - (only) ranking of subjects - Socially desirable answers - Interference with activities (diary) - Miscoding, misreporting..
30
Pros heart rate monitor?
Close relationship exercise Individual calibration curve Relatively cheap Information intensity/frequency/duration activity
31
Cons heart rate monitor?
HR affected by other factors (stress, ilness, drugs) Agreement with DLW poor -> particular in the range of low intensity PA
32
What motion sensors are there?
Pedometer, accelerometer
33
What does the pedometer do? Adv/disadv?
Count steps Pros Small/cheap Cons Lack sensitivity Very limited utility estimating EE
34
What does the accelerometer do? Adv, disadv?
Measure acceleration Adv Measures amount & intensity Small, cheap Disadv Not all activity (cycling, upper body etc) Estimatin EE = poor - promising