Relationships between human thirst, hunger, drinking, and feeding

Abstract

There is a widely held view that hunger prompts feeding to ensure energy needs are met, while thirst cues drinking to address hydration requirements. However, recent changes in the nature of the food supply and eating patterns have raised questions about the functionality of these relationships with respect to maintaining energy balance. The increasing consumption of energy-yielding beverages and foods with diluted energy density, through the use of ingredients such as high-intensity sweeteners and fat replacers, poses new challenges to presumed homeostatic energy regulatory mechanisms. This review draws on findings from a recent observational study and other published evidence to explore whether shifts of food composition and use patterns may be disrupting relationships between thirst, hunger, drinking, and eating, resulting in positive energy balance (e.g., drinking low satiety, energy-yielding beverages in response to hunger). The observational study entailed collecting hourly appetitive ratings and dietary recalls from 50 adults for seven consecutive days. These data reveal a clear bimodal daily hunger pattern, whereas thirst is stronger and more stable throughout the day. Further, approximately 75% of fluid intake occurs peri-prandially, with the majority derived from energy-yielding beverages. While there is published evidence that drinking is responsive to feeding, support for the view that drinking is the more tightly regulated behavior is stronger. Our data indicates that, due to a number of plausible factors, neither absolute values nor changes of hunger or thirst are strong predictors of energy intake. However, it is proposed that stable, high thirst facilitates drinking, and with the increased availability and use of energy-yielding beverages that have low satiety properties, can promote positive energy balance. There are marked individual differences in mean daily hunger and thirst ratings with unknown implications for energy balance.

Figure 1

Group mean hourly thirst ratings across a 7-day period, from 09:00-21:00h (n = 50).

Figure 2

Group mean hourly hunger ratings across a 7-day period, from 09:00-21:00h (n = 50).

Figure 3

Group correlation coefficients between days of the week for thirst across a 7-day period, from 09:00-21:00h (n = 50).

Figure 4

Group correlation coefficients between days of the week for hunger across a 7-day period, from 09:00-21:00h (n = 50).

Figure 5

Correlations between mean self-reported thirst following ingestion of 300kcals of apple juice, applesauce, or whole apple as a meal component or alone as a snack by 20 (10 male, 10 female) lean and 20 (10 male, 10 female) obese adults.

Figure 6

Correlations between mean self-reported hunger following ingestion of 300kcals of apple juice, applesauce, or whole apple as a meal component or alone as a snack by 20 (10 male, 10 female) lean and 20 (10 male, 10 female) obese adults.

Figure 7

Panel A - Range of mean daily thirst ratings (between 09:00 and 21:00 h) for each individual (n=50). Each plotted bar represents the highest and lowest daily mean thirst rating experienced over a consecutive 7-day period. Panel B - Mean of the ranges of daily thirst ratings (between 09:00 and 21:00 h) for each individual (n = 50). Each plotted bar represents the mean highest and lowest daily thirst rating experienced over a consecutive 7-day period.

Figure 8

Panel A - Range of mean daily hunger ratings (between 09:00 and 21:00 h) for each individual (n=50). Each plotted bar represents the highest and lowest daily mean hunger rating experienced over a consecutive 7-day period. Panel B - Mean ranges of daily hunger ratings (between 09:00 and 21:00 h) for each individual over a consecutive 7-day period (n = 50). Each plotted bar represents the mean highest and lowest daily hunger rating experienced over a consecutive 7-day period.