Assessment of Energy Expenditure Flashcards
state the 3 components of energy expenditure (and their relative percentages of TDEE)
- Physical activity = 10-15 %
- Diet induced thermogenesis (DIT) / thermic effect of food (TEF) = 10 %
- basal metabolic rate (BMR) = 65-75 %
state what it is meant by the key term - diet induced thermogenesis (DIT) / thermic effect of food (TEF)
the increase in metabolic rate after ingestion of a meal (everything from consuming to digestion to absorption)
state what it is meant by the key term - basal metabolic rate (BMR)
Basal metabolic rate is the rate of energy expenditure per unit time by endothermic animals at rest
how do you convert between a MJ and a Kcal
MJ = Kcal x 239
how do yo convert between a Kj and a Kcal
KJ = Kcal x 4.2
what is BMR dictated by ?
BMR is dictated by body size (Kg)
state what it is meant by the key term - direct calorimetry
Direct calorimetry measures the heat production of an individual, in calories, when placed in an insulated chamber where the heat is transferred to surrounding water
state 2/4 issues with the use of direct calorimetry
- can’t measure rapid changes
- the friction developed by an ergometer would contribute to the total heat produced during exercise
- not all the heat produced during exercise ay be immediately liberated from the body
- cannot determine which fuel is being utilised at one time so only measures metabolic rate
*therefore, not suitable for use during acute exercise
state what it is meant by the key term - indirect calorimetry
indirect calorimetry calculates heat that living organisms produce by measuring either their production of carbon dioxide and nitrogen waste, or from their consumption of oxygen
what is the usual piece of equipment used in the lab when doing indirect calorimetry
Douglas bag
state what it is meant by the key term - Douglas bag
an inflatable bag used to collect expired air for the determination of oxygen consumption and basal metabolic rate
what are the two main ways of predicting BMR with the use of age, height and weight ?
- Schofield equations (UK)
2. Harris-Benedict equations (US)
what is the Harris Benedict BMR equation for males ?
males = 66.47 + 13.5 (BW in Kg) + 5 (height, cm) - 6.76 (age)
what is the Harris Benedict BMR equation for females ?
females = 65.1 + 9.56 (BW in Kg) + 1.85 (height, cm) - 4.68 (age)
what is the Schofield equation for BMR in males aged 18-30 ?
(0.048 x Kg) + 3.653
what is the Schofield equation for BMR in females aged 18-30 ?
(0.062 x Kg) + 2.036
what is the Schofield equation for BMR in males aged 30-60 ?
(0.048 x Kg) + 3.653
what is the Schofield equation for BMR in females aged 30-60 ?
(0.034 x Kg) + 3.538
state 4 limitations of portable indirect calorimetry
- expensive
- inconvenient
- alters behaviour
- cannot be worn for extended periods
state what it is meant by the key term - double labelled water (DLW)
doubly labeled water (DLW) can be used for a method to measure the average daily metabolic rate of an organism over a period of time
what is the error of DLW relative to direct calorimetry
DLW has a 1-5 % error relative to direct calorimetry
when was DLW first used in mice, and when was it first used in humans ?
- mice - 1955
2. humans - 1980
explain, in 4 steps, the theory behind the use of DLW
- based upon use of stable heavy isotopes of H and O
- when 2.H (deuterium) and 18.O are introduced into the body, they mix with the normal H and O in the body
- the 18.O is lost more rapidly than 2.H as is lost in CO2 and H2O whereas 2H is only lost as H2O
- the difference in the rates is used to calculate CO2 production
state 3 disadvantages over the use of DLW
- high cost of equipment and very specialised staff are required for analysis
- assumed RER/RQ
- no info on the components of energy expenditure
explain (2 points) why assuming RER/RQ is a disadvantage of the use of DLW
- assumes RQ of 0.8 or 0.85
2. could lead to error
explain how the inability to gain info on the components of energy expenditure is a disadvantage over the use of DLW
total TDEE is the only thing measured - can combine with other measurements to obtain the other components (eg - BMR from indirect calorimetry)
what is the issue with the use of DLW for physiologists ?
DLW provides no info on the pattern or intensity of physical activity
state 4 facts about ‘activity diaries’ and ‘recall questionnaires’
- mostly self reported, can be experimenter administered
- usually utilise 10-15 min recording periods in the day
- many, many different recall questionnaires
- use either an activity score or a MET value for recorded activity to estimate EE
who came up with, and when did they come up with, the ‘compendium of physical activity’ ?
Ainsworth et al, 1993, 2000, 2011
why was the ‘compendium of physical activity’ designed ?
it was designed to increase the comparability of results from ‘reported PA’s’
state 3 introductory facts about the ‘compendium of physical activity’
- compromised from a variety of published an un-published sources
- element of subjectivity in both the initial record of activity by the participant and the coder
- uses averages of values for various activities
state 2 facts about using the compendium
- 1 MET= basal metabolic rate
- therefore, the multination of a MET by time will estimate EE
- eg) 1.5 Kcal/min (BMR) x 3 METs = 4.5 Kcal/min. ANS x 15 = 67.5 Kcals
state 2 facts about Pedometers and Accelerometry (pro and con)
- both very good at predicting energy EE during ambulatory activities (eg - running and walking)
- doesn’t pick up data from non-ambulatory activities (eg - cycling)
what is the purpose of the use of HR monitors in EE ?
HR monitors aim to pick up information that accelerometry may miss
what is HR estimate of EE based off ? (2 points)
- based off the linear relationship between HR and EE
2. linearity lost at low intensities, however
state 2 additional facts about HR monitors and EE
- required individual calibration
2. other factors can influence HR (eg - stress)
state 2 types of ‘multi sensory physical activity monitors’
- actiheart
2. sensewear armband
state 2 facts about ‘actiheart’
- actiheart tech uses a combination of HR and accelerometry data
- as sources of error are different for the two methods, this should - theoretically - be more precise
state 3 facts about ‘sensewear armband’
- worn on the upper arm
- has measures of heat flux, bi-axial accelerometer, skin temp, etc…
- the calculation for measuring EE are proprietary
what does it mean when it says the methods for calculating EE by ‘sensewear armbands’ are ‘proprietary’ ?
we don’t know how the algorithm works, we just trust the validity research
