midterm 1 review Flashcards
how much energy is used as heat
Gross Nrg: total available nrg (chem nrg) in food
Net Nrg: nrg available to the animal after metabolic
processes of digestion, absorption, excretion
• animal will use some nrg for heat (about 55-60%)
• animal will capture rest to nrg in high-nrg phosphate
bond (eg, ATP, creatine phosphate, phosphoenol
pyruvate) which eventually is liberated mainly as heat
• Digestible Energy (DE)
– DE in monogastrics = GE - fecal energy (BC)
The Respiratory Quotient (RQ)
The Respiratory Quotient (RQ)
ratio of CO2 produced : O2 consumed
- can be calculated using either the volumes or mols of O2 and CO2
Use of Biological Oxidation Data:
1. Determine, from O2 consumption, EE of an animal
(ie,Metabolizable Energy Expenditure)
2. If RQ is close to 0.7, can predict FAs are main fuel being [O]
- never be quite as low as 0.7; “obligate glu users”
3. If RQ is close to 1.0, can predict glu (hence CHO) is the main
physiological fuel being [O]
4. If RQ is between 0.7 - 1.0, you cannot predict, with this data
alone, the “mix” of fuel being [O]
Estimated Energy Requirement
EER
A level of dietary energy intake sufficient to
maintain a stable healthy body weight and an
adequate level of physical activity
• Differs from EAR in that it is not a distribution
of intakes (bell curve) reflecting physiological
variability
• Resting Metabolic Rate (RMR):
energy
expenditure under resting conditions. Somewhat
higher than BMR due to recent food intake or
recent activity.
Total Energy Expenditure (TEE):
sum of basal
energy expenditure, thermic effect of food,
physical activity, thermoregulation, and energy
expended in depositing new tissues and
producing milk (lactation).
Energy Intake is mesureed by
Food Freq. Quest. (FFQ)
• 24h Recall
• Food Records
• Food Weighin
Energy Expenditure
Direct Calorimetry • Indirect Calorimetry • Heart Rate Monitoring • Estimated from Activity – Motion sensors – Activity diary – Direct observation • Doubly labeled water (D2 18O)
Selection of Indicators for Estimating
Energy Requirement
- Reported Energy Intake
• Reported energy intakes of weight-stable
individuals could be used to predict energy
requirements for weight maintenance
• Limitation: reported energy intakes in dietary
surveys underestimate usual intake (can range
from 10-45% below actual intake) - Factorial Approach
• Used to set previous RDA
• Calculates TEE using activity info in 24 h period
and energy costs of each activity
• Limitation: not feasible to measure energy cost
of all ADLs
• Factorial method may underestimate energy
needs
Selection of Indicators for Estimating
Energy Requirement - Measurement of EE by Doubly Labeled Water (DLW)
• Used to set EER
• Relatively new technique in humans
– However, proposed and developed by Lifson (1950-1960s) for use in
small animals
• Adapted and now extensively used in humans (Schoeller et al.,
1986)
• Uses stable isotopes H2
18O and 2H2O
–
2H2O relates to water flux
– H2
18O relates to water flux plus carbon dioxide production
– These isotopes also can be used independently to measure TBW using
the principles of dilution
DLW Approach
Subject drinks known amount of the 2 stable isotopes of
water
• Isotopes mix with the body’s water
2. Sample periodically (over 3 weeks) a body fluid (i.e., urine or
blood) to measure disappearance of isotopes
•
2H2O is lost from the body only as water
• H2
18O is lost from the body in water and as C18O2
3. The difference between the 2 disappearance rates is an
index of body’s CO2 production
4. Predict TEE from a measurement of CO2 production
• Knowledge of composition of the diet
• Use standard indirect calorimetric techniques (RQ = ratio of
CO2 produced and O2 consumed)
Advantages of the DLW Method
Allows measurement of energy output under
normal, everyday conditions
• Represents patterns of energy expenditure
over several days
• Reflects differences in BMR during the day
and night/sleep
• Includes the energy cost of all physical
activities
DLW Database (Inclusion Criteria)
0-2 y wt-ht percentiles between 3rd and 97th
3-18 y BMI percentiles between 5th and 95th
>18 y BMI 18.5 – 24.9
DLW Database (Exclusion Criteria)
• Studies manipulating energy intake or
expenditure
• Elite groups: soldiers, astronauts, athletes
• Individuals with a PAL > 2.5 (PAL=TEE/BEE)
2 Compartment Model
body fat
– fat-free mass (FFM)
• FFM = body wt – body fat (fat mass); LBM = body wt – adipose fat
• LBM includes essential fat (e.g., cell membrane fat)
• often FFM = LBM in literature
6 Compartment Chemical Model (Brozek et al. 1963)
– aqueous - includes ECW, ICW – mineral - osseous - extraosseous – organic - glycogen (negligible) - protein - fat
Elemental Model
body weight consists of 11 elements which comprise >99% of body
weight in living subjects
i.e., C, N, Ca, Na, Cl, K, H, P, O, S, Mg
why is weight usefull
Weight • Useful for extremes – 300 lbs or 80 lbs for an adult female – 140 lbs ??? • Monitoring change – sudden gains or losses in weight
