Procedure

Upon recruitment, participants completed an online demographics and screening questionnaire. Participants were scheduled to complete the eating session for either a lunch (11:00am or 1:00pm) or dinner (5:00pm or 7:00pm) eating session in groups of 2 to 4. Prior to arrival, participants were randomly assigned to either the kilocalorie information given or the no kilocalorie information given condition using an online randomization tool. Participant condition placement was fully randomized, without consideration of demographic or physical differences. Upon arrival, their height and weight were measured. The WHR of each participant was measured using a MyoTape™ (Accu-Measure, Greenwood Village, CO) tape measure. Waist circumference was measured by wrapping the tape measure around the smallest circumference section of the abdomen. Hip circumference was measured by wrapping the measure around the widest circumference section of the buttocks. The measure was adjusted snugly, but so as not to cause compressions on the skin. Measurements were taken to the nearest half-inch. Participants were then led to an on-campus dining hall.

At the dining hall, the participants were instructed by a pair of undergraduate assistants to eat as much as they liked. To allow portion size and food selection to vary, participants were allowed to choose any of the food items in the dining hall available that day, and to go back for as many courses as they wished. The dining hall had a wide variety of foods to choose from, including items that were available daily, such as a salad bar, a pizza and pasta bar, and a sandwich station, and many other items that varied day to day. Participants’ food choices were not restricted in any way, other than by what was available in the cafeteria. Participants were allowed to select kilocalorie beverages (such as sweet tea and soda). Participants consumed their meal at an instrumented table (Figure 1). Video cameras were mounted in the ceiling above each participant which recorded the eating session. A course was defined as the time between the participant sitting down with food, prompting the experimenters to begin the recording process, and the participant getting up from the table, either to get another course or to end the session. Video recording was stopped between courses and restarted once the participant had been reseated for the next course. Upon sitting at the table with food, the tethered Bite Counter was placed on the participants’ dominant wrist, which was determined by self-report. Participants were instructed to eat and interact as naturally as possible, and to facilitate this, their eating behavior was not restricted in any way to accommodate for the Bite Counter; they were allowed to use napkins and eat with whichever hand they preferred, regardless of Bite Counter position.

The instrumented table. Each station has a tethered bite counter and a camera mounted in the ceiling to record the meal.

After each participant had made their food selections, an undergraduate assistant wrote down each food item, the portion size, and any customization made to the item (for example, adding condiments). Assistants used a menu provided by the dining hall that contained each food item that was supposed to be served in the cafeteria that day, along with a reference portion size for each item and kilocalorie content for that portion (e.g., 1 cup of seasoned corn contains 103 kilocalories) to cross-check the participants’ selections.

Upon completion of the meal, participants were given a custom post-meal questionnaire which asked questions seeking to gather data on how the cafeteria setting and the Bite Counter influenced their eating patterns. These data are not reported in this manuscript. However, pertinent to this study, this questionnaire also asked participants to estimate their overall meal kilocalorie intake with the following sentence: “Please estimate the number of calories you just consumed.” Participants in the kilocalorie information given condition were given the daily menu with kilocalorie information for their session to assist them in their estimations. The no kilocalorie information condition did not receive this information. After completing the questionnaire, the participants were debriefed, which involved telling the participants that the purpose of the study was to compare their kilocalorie estimates to estimates derived from the Bite Counter and to improve the accuracy of the device. In addition, any questions they had were answered, and they were free to leave.