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law of conservation of energy
total energy of universe is constant
energy can't be created or destroyed
what can happen to energy
It can be stored or transferred
system
part of universe being observed
surroundings
everything else in universe
universe
system and surroundings
1st law of thermodynamics
any change in energy of system is accompanied by an equal and opposite change in energy of surroundings
delta E system =
- Delta E surroundings
energy intake =
Total energy expenditure
system internation units
standardized terms for measurement of energy, force, work, and power
work
force x distance
joules
newtons per meter
joule
SI unit for work and energy
US energy content
kilocalories
1 kilocalorie
4.184 kilojoules
power
work/time
watts
J/sec
watt
SI unit of power
what is used to measure work and power
ergometers
types of ergometers
bench step, cycle and treadmill
what kind of reaction is respiration
combustion
aerobic respiration
electron transfer to oxygen
oxygen reduced to water with concomitant
coupled ion translocation
generation of an electrochemical gradient
almost all of the reactions in the body are
exothermic
how does a bomb calorimeter work
sample of food burned
with oxygen
amount of heat released = temp rise
represents amount of energy in food sample
example of direct measure
calorimetric chamber
calorimetric chamber
closed system
water jacket
heat measured
how much water they manage to warm by 1 degree
what does indirect calorimetry measure
respiratory gases
during indirect calorimetry what happens to air flow and respiratory gas samples
continuously obtained and accurately analysed by gas analysers
what is derived from the measurements of indirect calorimetry
oxygen consumed and carbon dioxide produced
what variables do we measure and control in indirect calorimetry
O2 and CO2 content of air going in and air expired
volume of air expired over time
temp, pressure, humidity, water vapor pressure
RER
VCO2/VO2
what does RQ reflect
gas exchange at level of tissues
doubly labelled water step 1
O18 rapidly exchanges between oxygen in water and CO2
doubly labelled water step 2
oxygen recycled as water or CO2
doubly labelled water step 3
hydrogen leaves body mainly as water
doubly labelled water step 4
CO2 exhaled
O18 declines
2H stuck in water
doubly labelled water step 5
difference in turnover rate = measure of production rate for CO2
doubly labelled water step 6
gauge loss by taking saliva sample at day 14 and measuring ratio of water isotopes
doubly labelled water step 7
measures EE over prior 14 days not day to day
assumptions of indirect calorimetry
all O2 used to oxidize biodegradable fuel
all CO2 evolved is recovered
gas exchange non-acidotic, steady state, conditions
no time delay for evolution of CO2
unaccounted for energy loss is minor
error in caloric equivalents for weight loss/gain or O2, CO2 and N
HR-VO2 limitations
depends on persons endurance
intra-individual variability
flat slope of relationship at low expenditure
what is the solution to endurance capacity variance in HR-VO2
individual calibration curves
what kind of external factors cause intra individual variability
emotion, posture and environment
what is an accelerometer
small device that measures
- total volume of PA
- sedentary behavior
- time spent in different intensities
- EE
what does an accelerometer measure
acceleration
advantages of accelerometer
easy to use
applicable to children and wide range of adults
long data store
identifies non-wear
multiple placement sites
captures low movement and sedentary periods
disadvantages of accelerometer
some activities not captured
don't inform on body posture
participant burden
water resistant
requires software
how do 2 people of the same weight have different REE
RMR will be higher in the person with a higher fat-free mass
greater mass =
greater TEE
most TEE is made up of what
REE
how to determine Free fat mass
fat and water only images
from axially acquired T1-weighted whole-body MRI gradient echo sequence using 2 point dixon technique
Thermic Effect of Food (TEF)
area between energy expenditure and basal metabolic curves
diet induced thermogenesis
how is TEF measured
via indirect calorimetry
what percentage of total energy intake is TEF
10%
what things affect TEF
insulin resistance and obesity
TEF of glucose infusions is blunted in what type of men
insulin resistant
what are principal factors in regulation of TEF
insulin sensitivity and abdominal adiposity
what is better in habitual exercisers than in sedentary persons
the SNS responsiveness and TEF after during beta-AR stimulation
other factors that affect TEF
age decreases it
physical activity increases it
greater meal size increases it
meal comp
meal timing
what is the result of elevated blood concentration of FFAs
lipotoxicity and ectopic deposition of lipids in other tissues
what is critical for maintaining normal blood levels in muscles
efficient uptake and oxidation of FFAs
during constant load physical activity when is it easier to achieve steady state oxygen consumption
at lower, submaximal intensities
what is the result of higher intensities during constant load physical activity
it takes longer to achieve steady state oxygen consumption
cross over concept
shift from fat to CHO metabolism as exercise intensity increases
if the desire is to maximize fat oxidation
exercise should maximize total amount of fat oxidized
improved insulin sensitivity results in
improved fat oxidation
combination of resistance and aerobic exercise
reduction of insulin resistance and functional limitation
EPOC
excess post-exercise oxygen consumption
EPOC is the result of
elevated oxygen consumption and metabolism at rest after exercise as the body tries to reach pre-exercise state
benefits of regular exercise
increased FA ox, mitochondrial density
increased activity of enzymes in TCA and uptake, transport and ox of FA
increased lipolytic responsiveness to catecholamines
benefits of high-intensity exercise
REE increase 5-20%
increase EPOC and post-prandial O2 after exercise
suppress appetite
increase carb preference
increase EE over time period
BAT is inversely associated with
% body fat in humans
how much BAT in people
200g
why is there lots of potential BAT
it's resistant to activation
if BAT were active all day
may increase EE but not to level that'll decrease weight
BAT function
preserve core temp not burn calories
challenge of putative BAT activators
being effective under conditions other than cold exposure
oxygen consumption of shivering thermogenesis
5X BMR
how does shivering thermogenesis function
activate primary motor centre of posterior hypothalamus
causes muscle firbres to contract involuntarily
why does shivering produce heat
as no net work is performed
what is the consequence of long periods of shivering
muscle fatigue
what is the result of administering propranolol
decreased VO2 consumption after cold exposure by 26% no change in shivering
as propranolol inhibits NST response
decrease in EE interpreted to reflect extent of NST in non-blocked status
protein turnover
degradation of proteins into AA and resynth of new proteins
what part of EE in an organism is protein turnover responsible
15-20% BMR
NEAT
non-exercise activity thermogenesis
how much does NEAT vary daily
2000kcal
NEAT is important in what
human fat gain and obesity
NEAT is underpinned by
profound and subtle biology
NEAT is central to what
obesity epidemic
adolescent exposure to low dose THC disrupts what
energy balance and adipose organ homeostasis in adulthood
RED-S duration
chronic or acutely severe
what can cause RED-S in athletes
LEA
when does RED-S arise
insufficient EI consumption to support daily EEE
what does RED-S lead to
various physiological and psychological dysfunctions
metabolic flexibility in healthy metabolically normal persons
rapid and complete substrate switching occurs
metabolic flexibility in obese, pre-obese and post-obese individuals
blunted substrate switching from low to high fat burning capacity
metabolic inflexibility in pima indians
24H RQ was a family trait
metabolic inflexibility in caucasians
24H RQ 32% heritable
diet quality impact on energy balance in order
fruits, non-starchy vegetables, nuts, yogurt, fish, seeds
starches or sugars
meats, cheese, and eggs,
metabolic healthy obesity
expansion of total FM doesn't necessarily translate to metabolic abnormalities
