Iso-Analytical provides a full range of analytical services for customers wishing to determine Energy Expenditure using doubly labelled water. The Doubly Labelled Water (DLW) method uses the natural occurring stable isotopes of water (D₂O and H₂¹⁸O) to assess energy expenditure, body composition and water flux in humans and animals. The DLW method is entirely safe and non-restrictive, requires only periodic sampling of body fluids and is well suited for measurement of energy expenditure in free-living or hospitalized patients.

The basis of the DLW method is to follow the decline in enrichment of the stable isotopes of oxygen (oxygen-18, ¹⁸O) and hydrogen (deuterium, ²H) in body water after initial labeling of the body water pool. As oxygen-18 is lost from the body in the form of water and carbon dioxide (CO2), whereas deuterium is lost only as water, the difference in loss from the body reflects the CO2 production during the period. Because CO2 production is the result of fat, carbohydrate and protein oxidation, it is an index of energy expenditure.

We are able to undertake analyses on samples of urine, blood or saliva, although urine is most commonly used because of ease of collection from subjects. Following collection and prior to analysis samples (approx. 5 mL for urine) should be stored in plastic containers at -20 °C.

We will equilibrate the body fluid samples under controlled conditions with hydrogen for ²H analysis and carbon dioxide for ¹⁸O analysis. All determinations of isotope enrichment will be made using Europa 20-20 continuous-flow isotope ratio mass spectrometers.

View Example Laboratory Report for DLW analysis for Total Body Water composition.