WEEK 4 Energy expenditure and physical activity

Question 1

What is direct vs indirect calorimetry?

Answer 1

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

Question 2

What is the procedure of DLW and what is measured?

Answer 2

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.

Question 3

Formula for energy expenditure?

Answer 3

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

Question 4

What is the principle of direct calorimetry?

Answer 4

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

Question 5

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

Answer 5

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)

Question 6

What are two disadv. of calorimetry?

Answer 6

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

Question 7

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

Answer 7

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

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

Question 8

Pro’s of DLW?

Answer 8

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

Question 9

Cons of DLW?

Answer 9

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

Question 10

Assumptions for DLW?

Answer 10

> 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)

Question 11

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

Answer 11

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

Question 12

T(D)EE =?

Answer 12

Total (daily) energy expenditure

Question 13

What are the 3 components of TEE? %?

Answer 13

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

Question 14

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

Answer 14

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

Question 15

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

Answer 15

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

Question 16

What does DIT depend on?

Answer 16

• size of meal
• composition of meal
• texture of meal
• non-nutrient substances

Question 17

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

Answer 17

1 MET = basal (resting) metabolic state

Question 18

PAL = ? formula?

Answer 18

Physical activity level. PAL = TEE/BMR

Question 19

Difference MET and PAL?

Answer 19

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

Question 20

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

Answer 20

MET < 1,5

Question 21

Categorize PAL values from bed rest to very high activity level

Answer 21

< 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

Question 22

What is the formula of PAL?

Answer 22

PAL = TEE/RMR(or BMR)

Question 23

What is the formula of TEE?

Answer 23

TEE = PAEE + RMR(or BMR) + DIT

Question 24

What is the formula of DIT?

Answer 24

DIT = 10% of TEE

Question 25

What is the most variable part of TEE?

Answer 25

PA level

Question 26

What are the 4 methods to assess PA/EE?

Answer 26

• Indirect calorimetry & doubly labelled water
• Self reported methods
• Questionnaire
• Logs/diaries
• Heart rate monitor
• Motion sensors
• Pedometer
• Accelerometers

Question 27

Cons of indirect calorimetry?

Answer 27

Costly, labour intensive, specialized equipment
Restricted to small sample size
Non-free living

Question 28

Pros of self-reported methods?

Answer 28

• Low costs
• Large population
• Costumisable (choose time frame/specific exercise)
• Easy

Question 29

Cons self-reported measures?

Answer 29

• Poor correlation with EE (DLW)
• (only) ranking of subjects
• Socially desirable answers
• Interference with activities (diary)
• Miscoding, misreporting..

Question 30

Pros heart rate monitor?

Answer 30

Close relationship exercise
Individual calibration curve
Relatively cheap
Information intensity/frequency/duration activity

Question 31

Cons heart rate monitor?

Answer 31

HR affected by other factors (stress, ilness, drugs)
Agreement with DLW poor -> particular in the range of low intensity PA

Question 32

What motion sensors are there?

Answer 32

Pedometer, accelerometer

Question 33

What does the pedometer do? Adv/disadv?

Answer 33

Count steps

Pros
Small/cheap

Cons
Lack sensitivity
Very limited utility estimating EE

Question 34

What does the accelerometer do? Adv, disadv?

Answer 34

Measure acceleration

Adv
Measures amount & intensity
Small, cheap

Disadv
Not all activity (cycling, upper body etc)
Estimatin EE = poor - promising