Assessing Energy Metabolism Flashcards
3 components that add up to equal TEE:
- BMR
- TEF
- PA
BMR:
- basal metabolic rate
- the minimum amount of energy the body uses at rest to fuel basic cellular-level metabolic activities and to keep the heart, lungs, kidneys, and other organs functioning
TEF:
- thermic effect of food
- the amount of energy utilized in the digestion, absorption and transportation of nutrients
PA:
- includes the additional EE above BEE and TEF due to muscular activity and comprises minor physical movements (such as fidgeting) as well as purposeful gross muscular work or physical exercise
- EAT & NEAT
60-75% of TEE:
BMR
15-30% of TEE:
PA/AT
10-15% of TEE:
TEF
1600’s experimental scientists were able to prove that….
- respiratory gas exchange represented combustion
- organisms produced heat, require oxygen for life, combusted food as they released heat
- human + oxygen –> CO2 + H20
Who was first to document direct calorimetry, and what is it?
- Lavoisier
- the heat production of living organisms
Lavoisier used an ____ _____ in which he measured the ____ and ____ produced by a ____ ____.
- ice calorimeter
- CO2
- heat
- guinea pig
How was Lavoisier’s research with calorimetry important?
provided the impetus to directly measure EE during rest and PA
Direct calorimetry is done under ____ ____ conditions in _____ ____ that measure changes in _____ associated with the _____ released by a subject.
- controlled laboratory
- insulated chambers
- temperature
- heat
Describe human direct calorimetry:
- subject is placed in a sealed insulated chamber with an oxygen supply
- a known volume of water is circulated through a series of pipes located at the top of the chamber
- heat produced and radiated by the individual is absorbed by the circulating water
- the change in water temp. reflects the metabolic energy (calories) released by the subject
Calorie =
the amount of heat energy needed to raise the temperature of 1 g of water by 1 degree celsius
Direct measurement of heat production in humans has considerable ____ ____, but limited _____ ____.
- theoretical implications
- practical application
Pitfalls of direct calorimetry:
- expensive
- technically difficult
- formidable engineering expertise
- limitations placed on a subject’s mobility
- not for large scale or population studies
Indirect calorimetry:
measuring EE by measuring a proxy of heat loss such as O2 consumption or CO2 production during rest and steady-state exercise
Fuel + O2 –>
CO2 (indirect calorimetry) + H20 + heat (direct calorimetry)
Indirect calorimetry assumes that metabolic rate can be estimated by ….
measuring the rate of transformation of chemical energy into heat
In indirect calorimetry, the amounts of ____ and ____ exchanged in the lungs closely represent the ___ and _____ of these substances by the ___ ____.
- O2 and CO2
- use
- release
- body tissues
Indirect calorimetry: measuring a person’s ____ uptake during activities, researchers obtain an ____ yet _____ estimate of EE.
- oxygen
- indirect
- accurate
2 common methods of indirect calorimetry:
- closed circuit
- open circuit
Closed circuit =
respiration chamber
Open circuit =
- expired gas analysis
- carbon/nitrogen excretion
- isoptically labelled water
- respiration chamber