What is the doubly Labelled water technique?
What is the doubly Labelled water technique?
The doubly labelled water (DLW) technique measures total carbon dioxide production by observing the differential rates of elimination of a bolus dose of the stable isotope tracers, 2H (deuterium) and 18O. Combined with an estimate of the respiratory quotient, this yields an estimate of total energy expenditure.
How does doubly labeled water measure energy expenditure?
The method to measure energy expenditure with doubly labelled water is based on the difference between the apparent turnover rates of the hydrogen and oxygen of body water as a function of carbon dioxide production. The oxygen isotope is lost as water and as carbon dioxide, due to exchange in the bicarbonate pools.
What is deuterium dilution?
Isotopic dilution studies are the gold standards of TBW measurement. It is based on the principle of the Deuterium dilution technique, which involves administering a dose of isotope to a subject, allowing the isotope to equilibrate within the dilution volume (in this case TBW) before the dilution volume is determined.
Is doubly Labelled water expensive?
The doubly labeled water method, however, does not provide any information on the pattern or intensity of any one activity during that time but the overall average energy expenditure. This method is also expensive due to the cost of the 18O and it does require sophisticated mass spectrometric analyses.
What are examples of methods used in indirect calorimetry?
Indirect calorimetry systems estimate respiratory gas exchange as a surrogate for substrates consumed and produced during metabolism. This is done by one of 4 methods: confinement, closed-circuit, total collection, and open-circuit approaches.
Which is more accurate direct or indirect calorimetry?
Many say that indirect calorimetry is the more accurate measurement tool. It gives a precise calculation of heat, because it involves actual oxygen uptake to give the caloric burn rate. Direct calorimetry measures the heat output by the subject, through direct observation inside a calorimeter.
Why are doubly labeled water methods so popular?
The doubly labeled water method of measuring energy consumption is based on the estimation of the rate of CO 2 elimination from the body. It has become a popular method because of several distinct advantages: 1. It can be applied to free-living individuals; that is, the subject need not be restrained or confined to bed. 2.
How is doubly labeled water used to measure energy expenditure?
The doubly labeled water (DLW) technique was developed as a method for measurement of free-living energy expenditure in animals (Lifson and McClintock, 1966). The method has since been validated in many animal species (for summary see Roberts, 1989; Schoeller, 1988).
Is the doubly labelled water method safe for children?
These levels are not known to produce any toxic reactions or physiological effects and the method is sufficiently safe that it is routinely used in potentially vulnerable groups like children (including new-borns) and pregnant mothers.
What does IAEA doubly labelled water technique mean?
IAEA International Atomic Energy Agency Doubly labelled water technique to assess total daily energy expenditure Christine Slater, PhD Nutrition Specialist IAEA [email protected] IAEA In adults: Total Energy Expenditure = Total Energy Intake In children: TEE = Total Energy Intake – Energy used for growth
