ARS | Publication request: FAT MASS ESTIMATION IN INFANTS AND TODDLERS: COMPARABILITY OF TOTAL BODY WATER, TOTAL BODY POTASSIUM, TOTAL BODY ELECTRICAL CONDUCTIVITY AND DUAL- ENERGY X-RAY ABSORPTIOMETRY

Submitted to: Journal of Pediatric Gastroenterology and Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 16, 1999
Publication Date: N/A

Interpretive Summary: It is important for pediatricians to have accurate methods of assessing the body composition of the babies and toddlers they see, in regard to understanding normal growth and development. There is no single standard, however, in using a particular method with these patients. We wanted to compare the different methods, including total body water, total body potassium, total body electrical conductivity, and dual-energy X-ray absorptiometry. We performed repeated body composition measurements on 76 healthy infants at intervals until they were 2 years old, and measured their fat mass using the different methods. We found significant differences among methods at each age. After extensive analysis, we concluded that these methods of estimating body fat mass in infants and toddlers are not interchangeable, and they require further development and validation. This article supplies extremely useful information, based on the utilization and analysis of multiple assessment tools in a large population, that will redound to the benefit of many pediatricians in evaluating the growth and development of their patients.

Technical Abstract: Background: Accurate assessment of body composition in infants and children is fundamental to understanding normal growth and development. Validation of methods applicable to pediatric populations is needed. In the absence of a gold standard, we compared methods using total body water, total body potassium, total body electrical conductivity and dual-energy X-ray absorptiometry measurements for the estimation of body fat mass in infants and toddlers. Methods: Repeated body composition measurements were performed on 76 healthy, term infants at 0.5, 3, 6, 9, 12, 18 and 24 mo of age. Total body water was determined by deuterium dilution and converted to fat free mass. Total body electrical conductivity was used to measure fat mass. Total body potassium was estimated by whole body counting and converted to fat free mass. Dual-energy X-ray absorptiometry was used to estimate fat mass at 0.5, 12 and 24 mo only. Data were analyzed by repeated dmeasures ANOVA, followed by Bonferroni multiple comparisons at 5% level. Results: Significant differences among methods were encountered at each age (P=0.001-0.05). The rank order of the methods and the magnitude of the method differences were a function of age, but not gender or infant feeding mode. Wide limits of agreement imply that the methods are not interchangeable for group or individual measurements. Conclusions: Methods using total body water, total body potassium, total body electrical conductivity and dual-energy X-ray absorptiometry to estimate body fat mass in infants and toddlers are not interchangeable, and require further development and validation.