Association Between Hydration and Body-Fat Percentage in Children in Miami-Dade: Preliminary Data From the MetA-Bone Trial

Abstract Objectives Background: Children 9–13 years old in the US have suboptimal hydration status, with an average water intake of 496 mL/d (adequate intake for water is 2,100 mL/d in girls and 2,400 mL/d in boys, as per the Institute of Medicine). Studies have shown a significant inverse association between hydration status and body-fat percentage in children, although most studies failed to use Dual-X-Ray Absorptiometry Scan (DXA), the gold standard for body composition. Objectives: To associate total fluid intake, hydration status, and body-fat percentage in children 10–13 years from the baseline visit of the MetA-Bone Trial, a trial to test the effect of soluble corn fiber supplementation on bone metabolism. Methods Body-fat percentage was measured using DXA, total fluid intake (mL/day) was assessed from three 24-hour dietary recalls using the Nutrition Data System for Research (NDSR), and hydration status was objectively measured using Urine Specific Gravity (USG) via 24-h urine collections. Statistical analyses included descriptive statistics and linear regression performed with SPSS 26.0. Models were adjusted for age and sex. Results A total of 14 children (57.1% males) had complete data. Mean body-fat was 31.8 ± 8.53%, mean total water intake was 1634 ± 866 mL/day (54.5% were below the water adequate intake), and mean USG was 1.031 ± 0.023 (55.6% were dehydrated). Linear regression showed that total water intake and the objective hydration status were not significantly associated (β = 0.457; p = 0.216; adjusted for age and sex β = 0.461 p = 0.319). No associations were found between total water intake and body-fat percentage (β = −0.254, p = 0.452; adjusted for age and sex (β = −0.102, p = 0.758) or between objective hydration status and body-fat percentage (β = 0.009; p = 0.982; adjusted for age and sex β = −0.034; p = −0.094). Conclusions Most children did not meet the adequate intake for water and were dehydrated. Total water intake and objective hydration status was not significantly associated among them and to body-fat percentage. A higher sample size may be necessary to find an association between hydration, body-fat percentage in children. Funding Sources Funding was supported by the National Institute of Health (Eunice Kennedy Shriver National Institute of Child Health and Human Development, NICHD), grant number 1R01HD098589-01.