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Schoeller, D. A.

Publications and source records attributed to Schoeller, D. A..

5 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Natural abundance deuterium and 18-oxygen effects on the precision of the doubly labeled water method

The doubly labeled water method for measuring total energy expenditure is subject to error from natural variations in the background 2H and 18O in body water. There is disagreement as to whether the variations in background abundances of the two stable isotopes covary and what relative doses of 2H and 18O minimize the impact of variation on the precision of the method. We have performed two studies to investigate the amount and covariance of the background variations. These were a study of urine collected weekly from eight subjects who remained in the Madison, WI locale for 6 wk and frequent urine samples from 14 subjects during round-trip travel to a locale > or = 500 miles from Madison, WI. Background variation in excess of analytical error was detected in six of the eight nontravelers, and covariance was demonstrated in four subjects. Background variation was detected in all 14 travelers, and covariance was demonstrated in 11 subjects. The median slopes of the regression lines of delta2H vs. delta18O were 6 and 7, respectively. Modeling indicated that 2H and 18O doses yielding a 6:1 ratio of final enrichments should minimize this error introduced to the doubly labeled water method.

NASA Discipline Regulatory Physiology↗
NASA NTRS2000

Bioelectrical impedance analysis. What does it measure?

Bioelectrical impedance analysis (BIA) has been proposed for measuring fat-free mass, total body water, percent fat, body cell mass, intracellular water, and extracellular water: a veritable laboratory in a box. Although it is unlikely that BIA is quite this versatile, correlations have been demonstrated between BIA and all of these body compartments. At the same time, it is known that all of the compartments are correlated among themselves. Because of this, it is difficult to determine whether BIA is specific for any or all of these compartments. To investigate this question, we induced acute changes in total body water and its compartments over a 3-h period. Using this approach, we demonstrated that multifrequency BIA, using the Cole-Cole model to calculate the zero frequency and infinite frequency resistance, measures extracellular and intracellular water.

NASA Discipline Regulatory Physiology↗
NASA NTRS1997

Comparison of ground-based and space flight energy expenditure and water turnover in middle-aged healthy male US astronauts

Energy requirements during space flight are poorly defined because they depend on metabolic-balance studies, food disappearance, and dietary records. Water turnover has been estimated by balance methods only. The purpose of this study was to determine energy requirements and water turnover for short-term space flights (8-14 d). Subjects were 13 male astronauts aged 36-51 y with normal body mass indexes (BMIs). Total energy expenditure (TEE) was determined during both a ground-based period and space flight and compared with the World Health Organization (WHO) calculations of energy requirements and dietary intake. TEE was not different for the ground-based and the space-flight periods (12.40 +/- 2.83 and 11.70 +/- 1.89 MJ/d, respectively), and the WHO calculation using the moderate activity correction was a good predictor of TEE during space flight. During the ground-based period, energy intake and TEE did not differ, but during space flight energy intake was significantly lower than TEE; body weight was also less at landing than before flight. Water turnover was lower during space flight than during the ground-based period (2.7 +/- 0.6 compared with 3.8 +/- 0.5 L/d), probably because of lower fluid intakes and perspiration loss during flight. This study confirmed that the WHO calculation can be used for male crew members' energy requirements during short space flights.

STS Shuttle Project↗