Utility of Body Weight, Urine Color, and Thirst Perception (WUT) in Determining Hydration in Young Adults.

Objective: The primary aim of this study was to assess the efficacy of the weight, urine, thirst (WUT) framework in predicting dehydration after a body water manipulation protocol, while concurrently determining the individual and interactive contributions of the model components.
Methods: The total study sample was 93 participants (female, n = 47), recruited from two institutions. Phase 1 involved collecting daily hydration measures from free-living participants (Study 1, 58 participants for 3 days; Study 2, 35 participants for 7 days). Phase 2 entailed a two-hour passive heating protocol, where participants from Study 2 were randomly assigned to one of three groups that manipulated total body water over 24-hours using passive heating and fluid restriction. During each Phase, participants provided urine samples, underwent body mass measurements, and completed questionnaires pertaining to thirst perception. Morning and 24-hour urine samples were assessed for color, osmolality, and specific gravity. Differences between intervention groups, based on the probability of hydration status, were examined (ANOVA) and ridge regression analysis assessed the relative importance of variables within the WUT model.
Results: The study revealed significant differences among the intervention groups for predicted probability of dehydration, as determined by changes in body mass (p = 0.001), urine color (p = 0.044), and thirst perception (p < 0.001). Binomial ridge regression indicated that change in body mass (58%) and thirst perception (26%) were the most influential predictors of dehydration.
Conclusions: These data support use of an enhanced version of the WUT model, underscoring the significance of changes in body mass and thirst perception in the assessment of hydration status.
Competing Interests: Conflict of Interest and Funding Source: This study was funded in part by a Faculty Grant awarded by the School of Health and Human Sciences as the University of North Carolina at Greensboro and the Biotechnology High Performance Computing Software Applications Institute (BHSAI). WMA declares the following conflicts of interest: he serves on the advisory boards for My Normative and Emerja Corporation, the Medical and Science Advisory Board for the Korey Stringer Institute, and the Sport Advisory Council for the Wu Tsai Human Performance Alliance where he has received compensation either as part of his role on the respective boards, or as a consultant. WMA has previously received consulting fees/honoraria/compensation/grant funding/travel support from the following entities that is related to the submitted work: Gatorade, Samsung, BSX, QKC LLC, Clif Bar & Company, Danone Research Nutricia, Nobo Inc, and Onda Vision. WMA is also the owner of Adams Sports Medicine Consulting LLC with clients on topics related to the submitted work.
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