(Mis)Perceptions About Healthy Eating: Effects on Food Intake and Appetite in Men and Women

The laboratory study will be conducted at the Clinical Investigation Unit (CIU) of the Institute of Nutraceuticals and Functional Foods (INAF). Food-related variables (perceived healthiness and "fatteningness" of foods) will be manipulated during an ad libitum single-meal test. We will examine the effects of these variables on food intake and appetite sensations in male and female normal-weight and overweight/obese restrained and unrestrained eaters. Each participant will be tested on an individual basis, during a 2-hour experimental session (randomized sessions between 11:00 a.m. and 5:00 p.m.). Because participants might change their eating behaviors if they become aware of the true purpose of the study, deception must be used. Males and females will thus be recruited to participate in an ostensible market-research study involving a taste-rating task, and each participant will then be carefully debriefed at the end of the experiment.

Male and female normal-weight with a body mass index (BMI) ≥18.5kg/m2 and <25kg/m2 and overweight/obese with a BMI ≥25kg/m2, restrained and unrestrained eaters will be randomly assigned to one of three experimental conditions ("healthy," "diet," and "unhealthy"). A plate of about 1000 grams (g) of bite-sized oatmeal-raisin cookies will be presented to each participant. On average, one bite-size cookie is about 10g, which represents approximately 40 kilocalories (kcal) per cookie. The manipulation of healthiness and "fatteningness" perceptions of the oatmeal-raisin cookies will be performed verbally by the experimenter as follows. In the "healthy" condition, the description will emphasize nutritional characteristics (e.g., high in fibre, low in saturated fat and free from trans-fat), so the overall healthiness of the snack will be highlighted. In the "diet" condition, the description will emphasize the benefits of oatmeal fibre for weight management (e.g., helps to cope with hunger), thereby highlighting the weight-loss potential of the snack. In the "unhealthy" condition, the description will emphasize hedonic characteristics of the food and less healthy ingredients (e.g. gourmet cookies, contains butter and sugar), so some inherent unhealthy aspects of the snack will be highlighted.

Males and females involved in the study will be invited to participate in a market-research study investigating various dimensions of a new snack product. A telephone screening interview will first be conducted for all subjects interested in participating in the study to ensure that they meet our inclusion criteria, to facilitate randomization prior to the experiment session and to set the appointment with the participant. During this interview, each participant will be informed that this market-research study involves a taste-rating task in which they will taste and rate a new snack food. They will have to self-report their weight and height, and answer descriptive questions about inclusion criteria (e.g., history of health problems, current medications, liking of the tested food, and prior participation in studies). They will also have to complete the Restraint Scale to assess whether they exhibit behavioral and attitudinal concerns about dieting and weight control. Each participant will then be categorized as a restrained eater (≥12 in males and ≥15 in females) or unrestrained eater (<12 in males and <15 in females). Following the categorization established by the Restraint Scale and BMI calculation, each participant will then be randomly assigned to one of the experimental conditions, according to restraint and weight status (Note that randomization will be adjusted according to the measured BMI). The telephone screening interview will be conducted at least one week prior to the appointment at the CIU to ensure that having been asked about restraint and weight status will not affect participants' food intake and appetite sensations by making restraint and weight salient during the experiment. To standardize food intake and to insure that subjects have comparable baseline appetite sensations across experimental manipulations, participants will be asked to refrain from eating oatmeal-raisin cookies (tested food) for at least 24 hours prior to the experiment, and to arrive at the CIU for the appointment in a pre-meal state (i.e., at least 2 hours without food prior to the experiment). Because physical activity might have an impact on appetite sensations, participants will also be asked to refrain from doing any strenuous exercise at least for 24 hours before the experiment. Note that the experimenter in the study will strictly follow a detailed script when testing each participant to ensure that the testing will be consistent between all participants.