Energy intake consumed during the two test meals is shown in the . As with meal energy intake, the gram weight of food consumed at the test meals was also less in the water preload condition as compared with the no-preload condition (611±31 vs 663±36 g, respectively; P=0.023). Dietary energy density did not differ between the two test meals (water preload: 0.83±0.03; no water preload: 0.87±0.04, P=0.13). Participants consumed significantly less energy at the test meal after the water preload as compared with the no-preload condition (74±23 kcal difference in energy intake between the two conditions), which represented an approximate 13% reduction in meal energy intake. Energy intake and grams of food consumed at breakfast among male and female participants are provided in the . The relative reduction in meal energy intake following the water preload did not differ significantly between male and female participants (8%±5% vs 11%±5%, respectively; P=0.70), nor did it differ between those categorized as overweight vs obese (9%±6% vs 11%±5%, respectively; P=0.77) or between water consumers (mean daily water intake >304 g/day; 8%±5% reduction) vs non-water consumers (mean daily water intake <304 g/day; 12%±5% reduction, P=0.54). The percentage reduction in meal energy intake was not significantly associated with age (r=−0.10, P=0.64), body mass index (r=0.15, P=0.48), mean habitual water intake (r=0.23, P=0.32), or mean habitual total beverage consumption (r=0.04, P=0.88).
Energy intake at ad libitum test meals: after a water preload and without a water preload condition. * P=0.004 vs no water preload.
Energy intake at ad libitum breakfast meals after a water preload and without a water preload among male (n=7) and female (n=17) older adults
Habitual daily water consumption in this sample (304±121 g; approximately 10.6 fl oz) was less than the recently proposed guidelines of 20 to 50 fl oz/day for adults (20
). In addition, total daily beverage consumption was 1,553±143 g/day (approximately 54 fl oz), which represents approximately 50% of recommended total fluid intake (20
). Mean total energy content of beverages consumed was 313±36 kcal/day.
We observed that premeal water consumption reduces meal energy intake (74 kcal) among overweight and obese older adults, which is consistent with our previous work demonstrating that consuming approximately 2 cups of water before a meal reduced meal energy intake by approximately 60 kcal in nonobese older adults (14
). The mechanism(s) responsible for reduced meal energy intake following water consumption in older adults are unclear, but delayed gastric emptying (22
) may contribute by reducing hunger and promoting fullness (6
). Inasmuch as gastric emptying is a time-dependent phenomenon, it is unknown how the timing of premeal water consumption might modulate subsequent meal energy intake. Future studies are needed to address this important issue.
Our findings should not be extrapolated beyond an acute meal setting and the population studied. To obtain objective measures of food/energy intake, the breakfast meals were conducted in a laboratory setting; thus, it is possible that this setting may have influenced participant’s food intake. Finally, it is unknown whether the significant reduction in meal energy intake after water consumption would be sustained with increased habitual water consumption, and whether premeal water consumption would facilitate weight loss and maintenance. However, these preliminary findings may serve as the basis for justifying future larger-scale intervention studies in this area.