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ARS Home » Plains Area » Houston, Texas » Children's Nutrition Research Center » Research » Publications at this Location » Publication #113654
Title: ESTIMATION OF NEONATAL BODY COMPOSITION: ISOTOPE DILUTION VERSUS TOBEC

Author
item HASHIMOTO, KASUMASA - CASE WESTERN RESERVE
item Wong, William
item THOMAS, ALICIA - CASE WESTERN RESERVE
item UVENA-CELEBREZZE, JENNIFER - CASE WESTERN RESERVE
item HUSTON-PRESSLEY, LARRAINE - CASE WESTERN RESERVE
item AMINI, SAEID - CASE WESTERN RESERVE
item CATALANO, PATRICK - CASE WESTERN RESERVE

Submitted to: American Journal of Obstetrics and Gynecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: We wanted to compare methods of estimating the body composition, and specifically the body fat, of newborn infants. It is important to know the exact body composition of infants in order to find out whether there might be a related medical problem. For example, if the infant's tissues do not contain enough water, that could cause dehydration, which could lead to oshock. The gold-standard form of assessment of body composition in infants is total-body electrical conductivity, or TOBEC. The TOBEC method requires the use of a large, high-tech instrument to which the patient must be brought. The isotope dilution method is easier to use because it is a portable method. With this method, total body water (TBW) is estimated by having the subject drink water labeled with stable isotopes of oxygen and hydrogen, and then measuring the amount of isotope concentration in the urine. We wanted to make sure this isotope dilution method was as accurate as TOBEC. We examined 40 healthy term newborns and assessed their percentage of body fat via isotope dilution, and compared the results with those estimated by TOBEC. We found that isotope dilution is good for measuring a body's water content accurately, particularly using the oxygen isotope, but it is not as good a method to estimate a baby's body fat. These findings will help doctors in choosing the most accurate way of assessing the body composition and related health status of newborn babies.

Technical Abstract: Objective: To evaluate neonatal body composition determined by the isotope dilution method compared with the total-body electrical conductivity (TOBEC) method. Study Design: Forty healthy term newborns were examined. An oral dose of **18O- and **2H-labeled water was given, and the isotope concentrations in urine samples were measured by gas-isotope-ratio mass- spectrometry. Fat (F) and percent body fat (%F) estimated by isotope dilution were correlated with F and %F estimated by TOBEC. Results: Twenty-six infants successfully completed the protocol. TBW measured by isotope dilution of **18O and **2H was 2.44+/-0.36 kg and 2.49+/-0.35 kg, respectively (p<0.001). F and %F estimated by **18O and **2H, and TOBEC were 0.48+/-0.20 kg and 13.7+/-5.1%, 0.48+/-0.19 kg and 13.7+/-4.6% and 0.38+/-0.21 kg and 10.9+/-5.0%, respectively. Neither F nor F% estimates by isotope dilution showed good correlation with the TOBEC estimates (r=0.22-0.57). Conclusion: Because of the wide variation of water content in individuals, the isotope dilution method may not be the optimal way of assessing body composition, and specifically body fat in newborns.