Assessment of energy expenditure I Flashcards
What are the three overall components of energy expenditure?
Basal metabolic rate, DIT (dietary induced thermogenesis)/TEF (thermic effect of feeding) and physical activity
What % of energy expenditure does basal metabolic rate account for?
65-75%
What % of energy expenditure does DIT/TEF account for?
10%
What % of energy expenditure does physical activity account for?
15-30%
What can dictate BMR?
Mass/size
What does Brodys mouse to elephant curve show?
There is a strong and predictable relationship between body mass and metabolic rate (between different organisms)
What does direct calorimetry rely on?
The fact that the total heat loss is equal to the rate of energy utilisation when the body temp is constant
How can direct calorimetry be measured?
Put an animal inside a chamber and surround the chamber with a water jacket. Measure the change in temperature of the water
What are some problems with direct calorimetry?
Can’t monitor rapid changes, can only measure resting situations, cant account for friction
What problem regarding substrate use is there with direct calorimetry?
Can’t determine which fuel is being used at any one time, only determine metabolic rate
What is one alternative to direct calorimetry?
Measuring gas exchange during a period of time
Why is measuring gas exchange a viable method for assessing energy expenditure?
Oxygen is used as a substrate for metabolism while carbon dioxide is produced
What kind of calorimetry is using gas exchange to measure energy expenditure?
Indirect calorimetry
What is used to do indirect calorimetry?
Douglas bags
Which component of energy expenditure is typically measured using indirect calorimetry?
basal metabolic rate
What do the Schofield and Harris-Benedict equations calculate?
Basal metabolic rate
What is fed into the Schofield and Harris-Benedict equations?
Body weight, depending on sex
How is the energy expenditure of exercise measured?
Exercising while doing indirect calorimetry
When doing indirect calorimetry during exercise, when must the oxygen uptake be measured?
During steady state
What is steady state of oxygen uptake during exercise?
A phase when the oxygen uptake is fairly constant
Possible issues with using indirect calorimetry as an absolute measure of energy expenditure during exercise?
Someone may be “exercising” (i.e., walking or general movement) when not connected to the machine, so you’d get an underestimate
Method of assessing energy expenditure over 24hrs?
Room calorimetry or whole-body calorimetry
What kind of calorimetry are room calorimetry or whole-body calorimetry?
Indirect
What does room calorimetry or whole-body calorimetry entail?
Subject being put into a sealed chamber for a few days, and the gas exchange is measured
