nutrition2 Flashcards
what is energy
the capacity to do work
what is energy balance
energy intake - energy expenditure
the amount of dietary energy added to or lost from the body’s energy store after the body’s physiological systems have done all their work for the day
energy balance concept
in balance- energy in = energy out - stable body mass
positive balance- energy in > energy out - body mass gain
negative balance - energy in < energy out - body mass loss
what is energy intake ?
the metabolizeable energy content of food expressed as kcal
what is energy expenditure?
fuels metabolized to support resting metabolic rate 60-80 %, thermic effect of food 6-10% and physical activity 10-30 %
what is energy availability?
energy intake - exercise energy expenditure
45 kcal/kg/day available to support non-exercise physiological functions
if EA <30 health status compromised
during weight/fat loss EA should be at 30-45
what do prospective methods do ?
provide information on dietary intake but rely on motivation and accurateness of subjects
different prospective methods are …
- diet surveys
- weighed food record
- duplicate food collections
- use of food analysis software/database
food records strengths
- simple
- fairly accurate (weighed foods more accurate )
- inexpensive
- longer periods needed for intake of fats, cholesterol and some micronutrients
food records weakness
- accuracy requires training
- highly motivated participant
- errors in estimating portion size when using household measures
- if unweighed: energy intake underestimated by 50 % and nutrients by 20 %
- after a week, bored less accurate
- women more competent
- dietary change when aware
what are retrospective methods?
provide information on past dietary intake
- diet history
- food frequency questionnaires
- dietary recall
strengths of dietary recall 24 h
-easy to administer
-time efficient
-inexpensive
low respondent burden
weakness of dietary recall
- may not represent usual food intake ( more accurate if repeated)
- underreporting
- memory bias
- underestimating energy and nutrient intake
types of gas exchange measurement
- resting
- activity
- whole room
what is the doubly labelled technique ?
subject ingests 2^H2^18O- 2^H excreted as H2O independent of metabolic rate
O18 as water and CO2 dependent on metabolic rate
urine analysis- difference btw excretion rates gives CO2 production
VO2=VCO2/RQ