Restricting fluid intake during a single meal did not affect food intake in older adults

Restricting fluid intake has been shown to decrease ad libitum food intake in animals and young adult humans. The purpose of this study was to determine if restricting fluid intake during a meal affects food intake in older adults. In a crossover counterbalanced design, 24 subjects (11 m, 13 f), 61-95 years, received lunch at a congregate meal site. Identical meals were accompanied by a volume of water equal to either 40% (restricted) or 100% (control) of each subject's usual lunch fluid intake. Pre-meal urine osmolality and specific gravity were used as indicators of hydration status. Weighed food intake was not different between the restricted and control conditions (400 g/2875 kJ and 408 g/2971 kJ, respectively). No significant correlations were found between urine osmolality or specific gravity and food intake, either in response to fluid restriction or per kg body weight. These results suggest that the appetite of healthy free-living older adults is not affected by fluid restriction during a single eating episode.