Overweight and Obese Children Aged 6-17 Years in China Had Lower Level of Hydration Status: A Cross-Sectional Study.

Objective: The aims of this study were to explore the differences in total body water and hydration status among Chinese children aged 6-17 years.

Methods: A cross-sectional study was implemented among children aged 6-17 years in China. The total body water (TBW), intracellular water (ICW), and extracellular water (ECW) were determined by bioelectrical impedance analysis (BIA). The participants were divided according to age-age 6-8 years, age 9-11 years, age 12-14 years, age 15-17 years-and body mass index (BMI) of China-underweight, normal weight, overweight, and obese groups. The differences of variables of groups were compared using analysis of variance, Student's t-test, and Kruskal-Wallis test. Significance levels were set at 0.05 (p < 0.05).

Results: A total of 59,643 participants (30,103 males and 29,540 females) completed the study. As children became older, the TBW, ICW, ECW, ICW/TBW, and TBW/FFM (TBW to fat free mass ratio) increased simultaneously (all p < 0.05); concurrently, the ECW/TBW decreased with age (all p < 0.05). Boys had higher TBW, ICW, ECW, ICW/TBW, TBW/BW, and TBW/FFM than those of girls at each age (all p < 0.05). For all BMI groups, increases in TBW, ICW, ECW were observed from the underweight group to the obese group, both in boys and girls (all p < 0.001). For the increase in BMI in all age groups, the values of TBW made a significantly lower percentage compared to BW. The higher BMI groups showed higher levels of TBW/FFM, both in girls and boys (all p < 0.001).

Conclusions: The body water contents of children aged 6-17 years varied according to their age, sex, and BMI. Overweight and obese individuals may have inferior hydration status compared to those with normal weight.