What is the doubly labeled water method?

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.

For what purpose would a researcher use doubly labeled water?

In particular, 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 (often also called the Field metabolic rate, or FMR, in non-human animals).

What is the main advantage of the doubly Labelled water technique?

Of these, doubly labeled water, the most accurate method, has the advantage of measuring energy consumption in a free-living individual over a prolonged period of time. Its disadvantages are expense and lack of availability.

What is direct and indirect calorimetry?

Direct calorimetry measures the heat output by the subject, through direct observation inside a calorimeter. Indirect calorimetry measure heat by using the variable of O2 consumption and manufactured CO2. Indirect calorimetry gives a more feasible and accurate measure of heat or energy, compared to direct calorimetry.

Is doubly labeled water safe?

The doubly labelled water method is considered safe for subjects of all ages, with no indications of health effects of the two isotopes at these concentrations (Leatherdale and Jones 1991). With regard to sample collection, body water enrichment for 18O and 2H is measured in blood-, saliva-, or urine samples.

What is the gold standard for measuring energy expenditure?

doubly labeled water
The doubly labeled water (DLW) technique is considered the gold standard for measuring energy expenditure in free-living individuals. However, the use of DLW is relatively expensive and typically is not feasible for large studies.

How accurate is doubly labeled water?

Later, validation studies, comparing doubly labelled water-assessed energy expenditure with simultaneously measured energy expenditure in a respiration chamber, showed that the method is accurate and has a precision of 2–8% (Schoeller 1988).

What is the main difference between direct and indirect calorimetry?

While direct calorimetry is achieved through direct measurement of total body heat produced, such as via a thermally sealed chamber, indirect calorimetry measures respiratory gases, i.e. oxygen (O2) and carbon dioxide (CO2) that are influenced by metabolism to meet energy requirements (Figure 1).

What is the principle of direct calorimetry?

Direct calorimetry obtains a direct measurement of the amount of heat generated by the body within a structure large enough to permit moderate amounts of activity. These structures are called whole-room calorimeters. Direct calorimetry provides a measure of energy expended in the form of heat.

Which instrument is used to measure the direct energy expenditure?

The direct calorimetry technique measures the rate of heat loss by the subject using a calorimeter. It is the most accurate method for quantifying metabolic rate [39], but its use is limited by the high cost.

What does doubly labeled water mean in Wikipedia?

From Wikipedia, the free encyclopedia Doubly labeled water is water in which both the hydrogen and the oxygen have been partly or completely replaced (i.e. labeled) with an uncommon isotope of these elements for tracing purposes.

What is the doubly labelled water ( DLW ) method?

What is the Doubly-Labelled Water Method? The doubly labelled water (DLW) method is an isotope-based technique for the assessment of energy expenditure. The method is based on the difference between the turnover rates of the hydrogen and oxygen of body water as a function of carbon dioxide (CO 2) production.

Why do we use doubly labeled water for energy expenditure?

The scientific basis that underlies the doubly labeled water method for estimating energy expenditure relies on the differential rates of loss of hydrogen and oxygen from the body at different levels of energy expenditure. Hydrogen is lost primarily in water, whereas oxygen is lost in both water and carbon dioxide.

What are the limitations of doubly labeled water?

Doubly labeled water Reference method Limitations Doubly labeled water Energy only Doubly labeled water Assumptions of model regarding water par Doubly labeled water Very expensive Doubly labeled water Analysis technically demanding