title: Total energy expenditure assessed by salivary doubly labelled water analysis and its relevance for short-term energy balance in humans.
abstract: BACKGROUND
  The doubly labelled water (DLW) method is a stable isotopic technique for measuring total energy expenditure (TEE). Saliva is the easiest sampling fluid for assessing isotopic enrichments, but blood is considered superior because of its rapid exchange with body water. Therefore, we compared a large range of isotopic enrichments in saliva and blood, and related TEE in subjects with their ad libitum total energy intake (TEI). The relevance of these parameters to body weight and fat change over an 8-day interval was also assessed.
  
  
  METHODS
  Thirty subjects underwent DLW analysis over either 8 or 14 days, during which time initial and final blood and saliva enrichments were compared. TEI was assessed by dieticians over the 8-day period only. Isotope ratio mass spectrometry was used for the measurement of δ(2)H and δ(18)O values.
  
  
  RESULTS
  No discrepancies were observed between sampling fluids over a wide range of enrichments. During the 8-day period, average TEI exceeded TEE by ~5% or less. Using saliva as sampling fluid, TEI and TEI-TEE, but not TEE, were positively correlated to body weight change. TEI-TEE and physical activity EE (AEE), but not TEI, correlated, respectively, positively and negatively to changes in fat mass.
  
  
  CONCLUSIONS
  The DLW method in humans can be reliably applied using saliva as sampling fluid. TEI-TEE as well as AEE contributes significantly to changes in fat mass over an 8-day period.
authors.affiliation: Center for Isotope Research (CIO), Energy and Sustainability Research Institute Groningen (ERSIG), University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.|Groningen Institute for Evolutionary Life Sciences (GELIFES), Unit Behavioral Neuroscience, University of Groningen, Nijenborgh 7, 9747, AG, Groningen, The Netherlands.
authors.forename: Stefano
authors.initials: S
authors.lastname: Guidotti
authors.affiliation: Center for Isotope Research (CIO), Energy and Sustainability Research Institute Groningen (ERSIG), University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.
authors.forename: Berthe M A A A
authors.initials: BM
authors.lastname: Verstappen-Dumoulin
authors.affiliation: Center for Isotope Research (CIO), Energy and Sustainability Research Institute Groningen (ERSIG), University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.
authors.forename: Henk G
authors.initials: HG
authors.lastname: Jansen
authors.affiliation: Center for Isotope Research (CIO), Energy and Sustainability Research Institute Groningen (ERSIG), University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.
authors.forename: Anita T
authors.initials: AT
authors.lastname: Aerts-Bijma
authors.affiliation: PRA International, Stationsweg 163, 9471, GP, Zuidlaren, The Netherlands.
authors.forename: André A
authors.initials: AA
authors.lastname: van Vliet
authors.affiliation: Groningen Institute for Evolutionary Life Sciences (GELIFES), Unit Behavioral Neuroscience, University of Groningen, Nijenborgh 7, 9747, AG, Groningen, The Netherlands.
authors.forename: Anton J W
authors.initials: AJ
authors.lastname: Scheurink
authors.affiliation: Center for Isotope Research (CIO), Energy and Sustainability Research Institute Groningen (ERSIG), University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.
authors.forename: Harro A J
authors.initials: HA
authors.lastname: Meijer
authors.affiliation: Center for Isotope Research (CIO), Energy and Sustainability Research Institute Groningen (ERSIG), University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.|Groningen Institute for Evolutionary Life Sciences (GELIFES), Unit Behavioral Neuroscience, University of Groningen, Nijenborgh 7, 9747, AG, Groningen, The Netherlands.
authors.forename: Gertjan
authors.initials: G
authors.lastname: van Dijk
mesh_terms: D000328:Adult; D003903:Deuterium / Q000032:analysis; D017666:Deuterium Oxide / Q000032:analysis*; D004734:Energy Metabolism / Q000502:physiology*; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D010103:Oxygen Isotopes / Q000032:analysis; D012463:Saliva / Q000737:chemistry*
chemical_list: D010103:Oxygen Isotopes; D003903:Deuterium; D017666:Deuterium Oxide