Total body water volume for white children and adolescents and anthropometric prediction equations: the Fels Longitudinal Study

BACKGROUND: There are few studies of total body water (TBW) volume in children. Such studies are needed, as are new prediction equations for the clinical management of children with renal insufficiency and those receiving dialysis. METHODS: Mixed longitudinal data were from 124 white boys and 116 white girls 8 to 20 years of age. TBW volume was measured by deuterium nuclear magnetic resonance spectroscopy, and random effects models were used to determine patterns of change over time. Sex-specific TBW prediction equations were developed using regression analysis. RESULTS: Boys had significantly greater (P < 0.05) mean TBW volumes than girls at all but 3 ages. TBW was significantly (P < 0.05) associated with age and maturation in the boys and the girls. In boys, mean TBW/WT varied from 0.55 to 0.59, while in the girls the mean declined from 0.53 to 0.49 by 16 years of age. Boys had significantly larger means for TBW/WT than girls, who had a significant, slight negative trend with age. The prediction equations were TBW = -25.87 + 0.23 (stature) + 0.37 (weight) for boys and TBW =-14.77 + 0.18 (stature) + 0.25 (weight) for girls. CONCLUSION: Means are provided for TBW in white children from 8 to 20 years of age, whose average fatness affected the percentage of TBW in body weight. These updated TBW prediction equations perform better than those available from the past.