Chronotype and physical activity associations with fluid and dietary habits in young adults

This study investigated the relationships between chronotype, physical activity, and fluid and nutrient intake in healthy young adults. A total of 935 participants (66.6% female), aged 18-30, were classified into morning, intermediate, or evening chronotypes using the Morningness - Eveningness Questionnaire. Physical activity was categorized as active or sedentary based on self-reported exercise frequency and duration. Nutrient intake was measured using 24-h dietary recall, a Food Frequency Questionnaire, and a structured fluid intake survey. Data collection occurred in June and July to minimize seasonal effects. Physically active individuals consumed significantly more water daily than sedentary participants (p < 0.001, η² = .088). They also reported higher intake of black tea, herbal tea, iced tea, Turkish coffee, and milk (all p < 0.001). Evening chronotype individuals consumed significantly less black tea and milk (both p < 0.001) but showed no significant difference in water intake (p = 0.088). Evening types were also linked to lower consumption of red meat (B = -0.38, p = 0.034) and fish (B = -0.58, p = 0.002), while the decrease in egg consumption was not statistically significant (p = 0.082). These results suggest that morning chronotype and physical activity correlate with healthier fluid intake patterns, whereas evening chronotype may reduce intake of some animal proteins. Overall, hydration and diet appear influenced by lifestyle and biological rhythms. The study highlights the need for personalized nutrition counseling that considers chronotype and physical activity to promote healthier behaviors.