Do Weight Status and the Level of Dietary Restraint Moderate the Relationship Between Package Unit Size and Food Intake?

The estimated prevalence of obesity among adults in 2007-2008 was 33.8% and the combined estimated prevalence of overweight and obesity was 68.0% [1]. Although there are no clear reasons for the current obesity epidemic, there is a general consensus that environmental dietary factors, such as package unit size, encourage excessive food intake and positive energy balance [2, 3]. It is believed that the package unit size of food indirectly influences food intake by impacting the accuracy of consumption monitoring [2, 4]. Large packages decrease the accuracy of consumption monitoring by making it difficult to assess how many servings have been consumed in one sitting, while small single-serving packages can increase the accuracy of consumption monitoring by providing a clear definition of what a standard serving is and how much one has consumed [2, 4, 5]. Therefore, it has been proposed that small, single-serving packages of snack foods may help reduce energy intake [4, 5]. To date, limited studies have been conducted in this area and the results are inconsistent [4-9]. Mixed results could be related to differences in participant variables, specifically weight status and level of dietary restraint (a term that refers to the amount of control exerted over food intake) [4, 9]. These individual characteristics may interact with food package unit size to influence one's food intake [2, 4]. Overweight individuals or restrained eaters may more closely monitor the volume of food they consume as compared to normal weight or unrestrained eaters [4, 9]. The [smaller] size of food packaging may aid in monitoring food consumption and thus, influence how much food is consumed in overweight and/or restrained eaters [2, 4]. Therefore, the objective of this study is to determine if weight status and the level of dietary restraint moderate the relationship between package unit size and food intake.

Specific Aims:

• Determine the effect of dietary restraint on the relationship between package unit size and food intake.
• Determine the effect of weight status on the relationship between package unit size and food intake.
• Determine the combined effect of weight status and dietary restraint on the relationship between package unit size and food intake.

Inclusion criteria

• Male and females aged 18-35 years old.
• Body Mass Index (BMI) between 18.5-24.9 kg/m2 or BMI between 25-39.9 kg/m2.

• For normal weight groups: BMI of 18.5-24.9 kg/m2.
• For overweight groups: BMI of 25-39.9 kg/m2.
• Dietary restraint scores of either less than or equal to 12 or > 12 on the Three Factor Eating Questionnaire-Cognitive Restraint scale (TFEQ-R) [10].

• For unrestrained groups: less than or equal to 12.
• For restrained groups: > 12.
• Do not have unfavorable preference toward pretzels.
• Do not have allergies to pretzel ingredients.
• Do not have a health condition or use medication that affects eating or requires a therapeutic diet.
• Must have a consistent schedule during the time of the study.
• Must agree to instructions to not share pretzel snack packages with others.

Exclusion criteria

• BMI below 18.5 or above 39.9 kg/m2.
• Have an unfavorable preference toward pretzels.
• Have allergies to pretzel ingredients (wheat flour).

• Severe allergies to nuts - Synder's of Hanover pretzels are made in a facility that handles peanut butter.
• Are unwilling to consume pretzels during the time of the study.
• Are pregnant or breastfeeding.
• Do not meet one or more of the other above mentioned eligibility requirements.