Comparison of estimated water requirements of adults across BMI and gender groups using continuous NHANES 1999-2004

There are no evidence-based guidelines regarding the estimation of water requirements for various subgroups of the population, including obese individuals. Gender and BMI are both factors that affect body composition and might be suspected to also affect water requirements. The purpose of this study was to compare the water requirements of male and female adults across BMI groups. Subjects were adults ≥19 years in the continuous NHANES 1999-2004. The measurement of total water intake (TWI) can be used as an estimate of an individual's water requirement. The TWI was determined from the 24 hour recall by totaling water consumed (g) from all dietary sources (food, beverages and plain drinking water). Two-way ANOVA tested for differences in TWI between genders and BMI groups (underweight, normal, overweight, and obese) using both age and kcal intake as covariates. Results show a significant interaction effect of BMI and gender (p <0.01). Overweight and obese males consumed more water than overweight and obese females (p < 0.05; p < 0.001, respectively). Underweight males consumed less water than normal-weight males (p < 0.05). Normal-weight males consumed less than overweight and obese males (p < 0.01; p < 0.0001, respectively). Underweight females consumed less than overweight and obese females (p < 0.05). These differences in TWI are suggestive of differences in water requirements between gender and BMI groups. Gender and BMI may need to be taken into account to accurately estimate the water requirements of various population subgroups.