title: Doubly labeled water measurement of human energy expenditure during exercise at high altitude.
abstract: Estimates of total daily energy expenditure (TDEE) by the doubly labeled water (DLW, 2H(2)18O) and intake balance (I-B) methods were compared in six male soldiers studied over 6 days that included 5 days of strenuous winter exercise at 2,500- to 3,100-m elevation. Use of body energy stores [-9.54 +/- 1.54 (SD) MJ/day or -2,280 +/- 368 kcal/day] was estimated from changes in body weight, body density (hydrodensitometry), and total body water (H(2)18O dilution). The subjects wore computerized activity monitors and kept daily records of ration consumption (9.87 +/- 3.60 MJ/day or 2,359 +/- 860 kcal/day). Accuracy of individual DLW and I-B TDEE values was estimated from the correlations of TDEE with fat-free mass (FFM) or total weight (body wt + load). The DLW and I-B estimates of TDEE differed by -12.0 to 15.2% but provided comparable estimates of group mean TDEE (DLW = 19.07 +/- 2.37 MJ/day or 4,558 +/- 566 kcal/day; I-B = 19.41 +/- 3.72 MJ/day or 4,639 +/- 889 kcal/day; P > 0.05). The DLW TDEE was correlated with both FFM (r2 = 0.89, P < 0.01, power = 0.95) and total weight (r2 = 0.95, P < 0.01, power = 0.99), whereas I-B TDEE was correlated only with total weight (r2 = 0.75, P < 0.03, power = 0.81). Under adverse field conditions the DLW method provided individual TDEE estimates that were probably more accurate than those provided by the I-B method.
authors.affiliation: US Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760.
authors.forename: R W
authors.initials: RW
authors.lastname: Hoyt
authors.forename: T E
authors.initials: TE
authors.lastname: Jones
authors.forename: C J
authors.initials: CJ
authors.lastname: Baker-Fulco
authors.forename: D A
authors.initials: DA
authors.lastname: Schoeller
authors.forename: R B
authors.initials: RB
authors.lastname: Schoene
authors.forename: R S
authors.initials: RS
authors.lastname: Schwartz
authors.forename: E W
authors.initials: EW
authors.lastname: Askew
authors.forename: A
authors.initials: A
authors.lastname: Cymerman
mesh_terms: D000204:Activity Cycles; D000328:Adult; D000531:Altitude; D001823:Body Composition; D002940:Circadian Rhythm; D003903:Deuterium; D004435:Eating; D004734:Energy Metabolism; D005069:Evaluation Studies as Topic; D006801:Humans; D008297:Male; D008889:Military Personnel; D010103:Oxygen Isotopes; D005082:Physical Exertion; D014867:Water
chemical_list: D010103:Oxygen Isotopes; D014867:Water; D003903:Deuterium