Energy Expenditure Flashcards
what is the first law of thermodynamics
energy is neither created nor destroyed, but instead, transformed from one form to another
what is a kilocalorie?
the amount of heat required to raise the temperature of 1 kg (liter) 1 degree C
what is a joule?
energy expended (work done) in applying a force of one newton through a distance of one meter
explain how direct calorimetry works
water (of a known constant temperature) passes from one ends of a jacket to the other; the temp of the water leaving the jacket is used to calculate energy expended
why don’t we use direct calorimetry
expensive
takes a lot of time to ensure there are no leaks/everything works properly
where do we still use direct calorimetry?
in bomb calorimetry with food
- food is lit on fire, the amount of heat it produces changes the temperature of the water
- nitrogen ash can be used to determine protein in food
direct calorimetry measures …
heat production
explain how indirect calorimetry works
O2 is needed to metabolize macronutrients and produce energy
the amount of energy released per liter of O2 consumed is specific for each substrate
if we can can accurately measure O2 consumption and CO2 production, we can estimate EE (we must know the substrate mix and RQ)
indirect calorimetry measures …
O2 consumption and CO2 production
RQ = __ / __
CO2 production / O2 production
RQ of carbs, fat, protein
carbs: 1.0
fat: ~0.7
protein: ~0.8
if we don’t have RQ, we would use ___
*5 kcal/liter O2 consumed
explain how doubly labled water works
a free living technique where the loss from the body of two isotopes reflects the CO2 production during the period
three other techniques for measuring energy expenditure (that are less accurate)
- heart rate
- accelerometer
- pedometer
define: RMR
the amount of energy required to keep the body functioning at rest plus the cost of arousal (i.e. breathing, blood circulation, body temp control, cell growth, brain/nerve function, heart function)
