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PURPOSE: Animal research suggests that variations in daily dietary macronutrient distribution may impact fluid consumption. However, this has not been fully investigated in humans. Thus, the purpose of this study was to determine the impact of dietary intake on fluid intake, thirst, and urinary hydration biomarkers. METHODS: Thirty-four participants (44% female; age: 23±4 years; height: 172.9±10.3cm; body mass: 77.2±18.1kg; body fat: 18.4± 8.4%) recorded their food and fluid intake, and provided a 24h urine sample over seven consecutive days. Urinary hydration biomarkers included urine volume (UVOL), urine osmolality (UOSM), urine specific gravity (USG), and urine color (UCOL). Each morning, participants completed two subjective ratings of perceived thirst; a 9-point Likert scale, and 100mm visual analog scales comprised of six indices (thirstiness, pleasantness, dryness, taste, fullness, sickness). RESULTS: Mean weekly macronutrient percentages and total calorie intake were used in multiple regression models as predictors of average total fluid intake, thirst, and urinary hydration markers. Throughout the week, participants reported consuming, on average, 1945±429 calories (36.5±4.4% fat, 44.3±6.3% carbohydrate, 18.5±4.5% protein) and 2508±1122mL fluid per day. Mean 7-day 24h urinary hydration markers were UVOL:1724±850mL, USG :1.017±0.005, UOSM: 565±212, UCOL: 3.89±0.99. Dietary intake that was higher in percentage of fat consumed was associated with higher ratings of "fullness" on morning thirst scale sub ratings (adj R² = 0.1181, p =0.0167). Consuming a greater proportion of calories from protein was associated with increased UVOL (adj R² = 0.1370, p = 0.0340). However, protein intake was not significantly associated with fluid intake (adj R2 = 0.0569, p = 0.2516), regardless of the type of fluid consumed (p > 0.05). UOSM, USG, UCOL and the other indices of thirst were not associated with macronutrient consumption (p>0.05). CONCLUSION: These results suggest increased consumption of dietary protein intake is associated with improved hydration status based on increased 24h urine volume, with the maintenance of other urinary hydration indices. Grant or Funding Information: This study was funded by a University of North Carolina at Greensboro Office of Research Engagement New Faculty Grant. [ABSTRACT FROM AUTHOR]

PURPOSE: Appropriate fluid intake is important to offset water losses induced by physical activity. However, limited research has investigated the relationships between physical activity and fluid intake in free living individuals. To assess the associations between objective and subjective measures of physical activity, reported fluid intake, and urinary hydration biomarkers in free living emerging adults. METHODS: Thirty-four participants (44% female; age, 23±4 years; height, 172.9±10.3cm; body mass, 77.2±18.1kg; body fat, 18.4± 8.4%) provided a 24h urine sample across seven consecutive days for measures of urine volume (UVOL), urine osmolality (UOSMO), urine specific gravity (USG) and urine color (UCOL). A validated fluid log was used to record fluid intake each day, where fluid intake was segmented into morning (waking - noon), afternoon (noon - 5pm) and evening (5pm - sleep). Physical activity was objectively assessed using wrist-worn actigraphy and analyzed using standard cutoffs. Subjective assessment of physical activity quantified day-level physical activity and was measured by MET-minutes. RESULTS: Over 7 consecutive days, participants participated in 16.97±23.42 minutes of moderate-to-vigorous physical activity (MVPA) and 677.89±702.62 MET-minutes of activity per day. Mean 7-day fluid consumption was 2551±1056mL and corresponding mean 7-day UVOL, UOSMO, USG, and UCOL was 1699±865mL, 567±210 mOsm/kg, 1.020±0.010 AU, and 3.9±1.0 AU, respectively. Increased MVPA (adj R² = 0.114, p = 0.044) and increased total MET-minutes (adj R² = 0.192, p = 0.005) was associated with decreased 24 h USG. Greater morning and evening fluid consumption was associated with increased 24h UVOL (adj R² = 0.589, P = 0.02; P < 0.0001). Greater evening fluid intake was associated with lower 24h UOSMO (adj R² = 0.331, P = 0.01). CONCLUSIONS: Increasing day-level physical activity in addition to consuming a greater volume of fluids in the morning and evening improved hydration status as reflected by 24h urinary hydration variables. Further work is needed to explore the associations between physical activity and timing of the fluids consumed. Grant or Funding Information: This study was funded by a University of North Carolina at Greensboro Office of Research Engagement New Faculty Grant. [ABSTRACT FROM AUTHOR]