OBJECTIVE: Experimental trials using test meals suggest that water promotes satiety and decreases subsequent intake, thus possibly working to prevent obesity, when it is consumed as an integral component of a food, but not when consumed alone or alongside a food. We examined the associations of intake of water from beverages and intake of water from foods with body mass index (BMI) and waist circumference in free-living humans consuming self-selected diets. METHODS: This observational cross-sectional study included 1136 female Japanese dietetic students 18-22 y of age. Dietary intake was assessed with a validated, self-administered, comprehensive, diet-history questionnaire. BMI was calculated using measured body height and weight. Waist circumference was measured at the level of the umbilicus. RESULTS: Means +/- standard deviations of BMI, waist circumference, intake of water from beverages, and intake of water from foods were 21.3 +/- 2.7 kg/m(2), 72.9 +/- 7.1 cm, 569 +/- 318 g/1000 kcal, and 476 +/- 110 g/1000 kcal, respectively. After adjustment for potential confounding factors, intake of water from beverages was not associated with BMI (P for trend = 0.25) or waist circumference (P for trend = 0.43). Conversely, intake of water from foods showed independent and negative associations with BMI (P for trend = 0.030) and waist circumference (P for trend = 0.0003). CONCLUSION: Intake of water from foods, but not water from beverages, was independently associated with lower BMI and waist circumference in free-living humans consuming self-selected diets.