Understanding the Effects of Water-related Appetite Expectancies on Caloric Intake in College Students

Understanding the Effects of Water-related Appetite Expectancies on Caloric Intake in College Students

Consuming large volumes of water has recently been identified as a common weight loss strategy among U.S. adults. It is a widespread belief that drinking water increases feelings of satiety and reduces food intake, which could contribute to long-term weight maintenance. Many studies have shown support for this, demonstrating water's ability to reduce hunger and energy intake. In some cases, increased water consumption was associated with weight loss. However, the mechanisms of how water affects food intake have been minimally explored. There is potential that the effect of water on reduced food intake and increased satiety is due to individuals' belief that water will reduce their appetite and food intake. The question remains if water expectancy has a meaningful influence on water's ability to reduce food intake. The investigators hypothesize that participants will report less hunger and consume fewer calories when given water and an expectancy that water will affect appetite, compared to a condition when given water and do not expect water to have an effect on appetite. We further hypothesize that calorie intake will not meaningfully differ when participants are given water with no expectancies compared to when given no water. During this experiment, the investigators will vary the presence of water and manipulate expectancies about water's effects on appetite across three conditions: (1) an expectancy and water condition; (2) an expectancy and no water condition; and (3) a no expectancy and water condition. In each condition, participants will engage in a bogus taste test and complete two short cognitive tasks for distraction purposes. In an effort to prevent demand characteristics, this study involves deception. Participants will be told that the research team is interested in testing the effects of three different mint herb variations on attention, coordination, and taste perceptions. After completing the cognitive tasks and taste test, participants will have a 10 minute period to eat as much of the remaining food as they'd like. Food will be weighed before and after this period (without the participant's knowledge) in order to determine caloric intake.

In the expectancy and water condition, participants will be instructed to consume the mint herb and 500mL of water before the start of the taste test. The script for this condition will inform them of research that has shown water to decrease appetite by up to 50% (attempting to create an expectancy).

Participants will be instructed to consume the mint herb and 500mL of water before the start of the taste test. The script will inform them of research that has shown water to decrease appetite by up to 50%. In this condition, however, the research team will also inform them that this herb is expected to counteract the effects of water on appetite because it decreases water retention, causing water to pass through the stomach and intestines at a faster than normal rate (attempting to create no water expectancy or nullify any pre-existing expectancy).

Participants will be instructed to consume the mint herb and 50mL of water before the start of the taste test. Participants will be given 100mL of water during the taste test to aid in their ability to taste and consume food, and to avoid acute thirst interfering with food consumption. Access to fluids during a taste test has been used in control conditions in similar studies. The script for this condition will inform participants of research that has shown water to decrease appetite by up to 50% but acknowledge that they will not be receiving water (thus, they should not expect an effect on appetite).

Four-question 100mm visual analog scale (VAS) assessing assesses hunger, fullness, satiety, and prospective food consumption. The minimum possible score is 0, and the maximum possible score is 100.

International Physical Activity Questionnaire (IPAQ-SF). Participants are categorized into low, moderate, or high levels of physical activity. Higher score indicates more physical activity engagement (better outcome).

Eating Disorder Examination Questionnaire (EDE-Q). The minimum possible score is 0 and maximum possible score is 34.5. A higher score indicates higher restrained eating symptoms (poorer outcome).

As part of the baseline questionnaire, participants will be asked about how many glasses of water they drank over the past 7 days in order to assess habitual water intake. Response options range from "I did not drink water during the past 7 days" to "4 or more glasses per day."

Inclusion Criteria: 18 - 65 years of age rating at least two foods from each category (chips/crackers and sweets/candies) on the food options list for the taste test as a 7 ("like moderately") or higher on a 9-point hedonic scale willing/able to come to the lab for three sessions Exclusion Criteria: current smoker self-report of a current or past eating disorder diagnosis taking an appetite suppressant or stimulant medication currently engaged in a weight loss program currently pregnant, breastfeeding, or planning to become pregnant allergy to mint

IPD will be shared on the Open Science Framework (OSF) platform following the completion of the study. The study protocol, statistical analysis plan, and de-identified analytic code will be available.

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