John R. SpeakmanYosuke YamadaHiroyuki SagayamaElena S.F. BermanPhilip N. AinslieLene F. AndersenLiam J. AndersonLenore ArabIssaad BaddouKweku Bedu-AddoEllen E. BlaakStephane BlancAlberto G. BonomiCarlijn V.C. BoutenPascal BovetMaciej S. BuchowskiNancy F. ButteStefan G.J.A. CampsGraeme L. CloseJamie A. CooperSeth A. CreasySai Krupa DasRichard CooperLara R. DugasCara B. EbbelingUlf EkelundSonja EntringerTerrence ForresterBarry W. FudgeAnnelies H. GorisMichael GurvenCatherine HamblyAsmaa El HamdouchiMarije B. HoosSumei HuNoorjehan JoonasAnnemiek M. JoosenPeter KatzmarzykKitty P. KempenMisaka KimuraWilliam E. KrausRobert F. KushnerEstelle V. LambertWilliam R. LeonardNader LessanDavid S. LudwigCorby K. MartinAnine C. MedinErwin P. MeijerJames C. MorehenJames P. MortonMarian L. NeuhouserTheresa A. NicklasRobert M. OjiamboKirsi H. PietiläinenYannis P. PitsiladisJacob Plange-RhuleGuy PlasquiRoss L. PrenticeRoberto A. RabinovichSusan B. RacetteDavid A. RaichlenEric RavussinRebecca M. ReynoldsSusan B. RobertsAlbertine J. SchuitAnders M. SjödinEric SticeSamuel S. UrlacherGiulio ValentiLudo M. Van EttenEdgar A. Van MilJonathan C.K. WellsGeorge WilsonBrian M. WoodJack YanovskiTsukasa YoshidaXueying ZhangAlexia J. Murphy-AlfordCornelia U. LoechlEdward L. MelansonAmy H. LukeHerman PontzerJennifer RoodDale A. SchoellerKlaas R. WesterterpWilliam W. Wong2025-03-042025-03-042021-02-1610.1016/j.xcrm.2021.100203https://dspace.ughe.org/handle/123456789/415The doubly labeled water (DLW) method measures total energy expenditure (TEE) in free-living subjects. Several equations are used to convert isotopic data into TEE. Using the International Atomic Energy Agency (IAEA) DLW database (5,756 measurements of adults and children), we show considerable variability is introduced by different equations. The estimated rCO2 is sensitive to the dilution space ratio (DSR) of the two isotopes. Based on performance in validation studies, we propose a new equation based on a new estimate of the mean DSR. The DSR is lower at low body masses (<10 kg). Using data for 1,021 babies and infants, we show that the DSR varies non-linearly with body mass between 0 and 10 kg. Using this relationship to predict DSR from weight provides an equation for rCO2 over this size range that agrees well with indirect calorimetry (average difference 0.64%; SD = 12.2%). We propose adoption of these equations in future studies. Keywords: doubly labeled water; free-living; total energy expenditure; validation.endoubly labeled waterfree-livingEnergy expenditureWaterHumanjournal-article