A Comparison of Satiety Effects Two Commercially Available Snack Bars

The study protocol is initiated after enrollment with a Food Frequency Questionnaire and a Three-factor eating questionnaire conducted during the screening visit after the participant's qualifications have been verified. After the questionnaires have been completed, the study visits and food pick ups are scheduled according to the availability of the subject and the study calendar. At the end of the screening appointment, the subject selects the frozen dinners to be consumed the evening prior to the study visit.

The study is a crossover design in which investigators will assess the immediate effects of a single meal of two commercially available snack bars on subjective feelings of satiety over 2 hours and on energy and nutrient intake from a subsequent meal 2:15 to 2:30 following consumption of the bars. Study visits will be scheduled between 1 and 14 days apart.

Subjects will consume a standard meal between 7 and 8 PM the evening prior to each study visit and complete a satiety questionnaire after finishing the meal. The subjects record all food consumed the day prior to the study visit including the dinner meals provided by the study. Participants will pick up food at the Indiana University-Bloomington School of Public Health the day prior to the scheduled study visits. This visit consists of dispensing the evening meals in lunch coolers packed with icepacks and the frozen meals the participant selected in the screening appointment. The study visit protocol for the following day is reviewed briefly. Appointment reminders are set up as emails and calendar invitations instructing the participant to consume the meals between 7-8 PM that night, to complete a satiety questionnaire, the link to which is embedded in the emails, and to remain fasted except for water and non-caloric beverages until the study visit the next day. Participants are offered a paper version of the satiety questionnaire if they so desire. The satiety questionnaire asks the participants to evaluate their feelings of hunger, fullness, desire to eat, and satisfaction with the previous meal. Desire to eat is differentiated to the participant as a desire to consume food regardless of their state of hunger while satisfaction is differentiated from fullness to the participants as a psychological sensation of contentedness and not a physical sensation of fullness. The same questionnaire is used for all time points during each study visit. Participants are asked to refrain from consuming caffeine in the morning. A specific arrival time is set for arrival at the Innovation Center the following day between 8 and 8:40 AM.

After the subject arrives at the IU-Bloomington Innovation Center, coolers and icepacks are collected, compliance with the study protocol is confirmed. Next the diet record is reviewed by study personnel. Participants may be asked to clarify entries made on the diet record.

Participants are invited to a room where as many as 3 participants at a time will undergo the study protocol. Subjects are allowed to interact with each other but are instructed to refrain from discussing the snack bars. A baseline satiety questionnaire is completed before the snack bars are offered with a bottle of water. Participants are instructed to enter "1" with regard to satisfaction with the meal at this fasted time point. Ad libitum water intake is allowed throughout the study visit. The participants are instructed to consume two snack bars comprising 300 kcal as quickly and comfortably as possible. After the subjects consume the bars, study personnel provide the participant with a sensory evaluation, either printed or electronic, which asks the subject to evaluate the bars in terms of overall taste, sweetness, saltiness, savory, desire to eat more, with the meal, and fullness/satiation. Participants complete the sensory evaluation after having consumed both bars. If participants are unable to consume both bars, the sensory evaluation is not completed, and the experimental protocol is terminated for that subject.

The subjects remain in the room are are allowed bathroom breaks, to entertain themselves with their own audio devices, to read, and to work. Participants are prohibited from bringing and consuming outside food and from exercising during the study protocol. Satiety questionnaires are completed every 30 minutes from fasting. An electronic timer is provided with a flow sheet denoting the times for the satiety questionnaires to be completed. Participants write the times that they completed each iteration of the satiety questionnaire. Participants are monitored periodically for compliance and electronic recording of the questionnaires is monitored.

After 2 hours the penultimate satiety questionnaire for the study visit is completed. Subjects are informed that they will be escorted to a lunch buffet consisting of grilled hamburger patties, grilled chicken, brioche buns, sliced tomatoes, sliced medium cheddar cheese, mayonnaise, mustard and ketchup, a fruit tray with individual portions of watermelon, cantaloupe, strawberries and blueberries, a bowl of potato chips, a bowl of mixed, salted nuts, chocolate chip cookies, and whipped cream to add to any of the food they choose. Participants are instructed to "serve themselves as much of the food as they care to consume and to consume it until comfortably full as quickly and comfortably as possible." Participants log the time that they finished the meals and complete a final satiety questionnaire after lunch. Each food item is weighed by study personnel before and after the participants dine.

A second study visit is conducted that mirrors the first with a different type of snack bar. Start times for the protocol and the buffet lunch are matched as closely to the first study visit as possible.

Statistical Plan (This plan was articulated in the proposal and agreed upon when the proposal was accepted, but was uploaded here on March 24, 2026)

This study will be conducted as a single-blind randomized cross-over design in which consented participants will be randomly assigned to two treatment orders (Tx 1 then Tx 2 or Tx 2 then Tx 1) according to a block randomization scheme created by the IU-Bloomington SPH Biostatistics Consulting Center. Enrolling 150 subjects, randomized to which diet is received first, and assuming 20% attrition, a sample size of 120 completers would provide 80% power for detecting significant differences (two-sided alpha=0.05) between the two diets in the crossover study for "medium" effect sizes, Cohen's dz=0.268. Rather than the classic d used for between-group comparisons, dz is the standardized difference from first calculating a difference score between each person's responses in each condition and computing dz=Mean(diff)/ SD(diff). This effect size is consistent with previous literature where dz was observed to be 0.49. From multiple other crossover studies using preloads and test meals, we conservatively estimate that standard deviations of within-subject differences in intake between conditions is around 150 kcal. This would imply that our study is powered to true mean differences even if the actual causal effect is as small as 39 kcal.

The statistical plan includes the crossover data as described by Senn utilizing the intent-to-treat (ITT) principle methodology previously described [7] which will include all randomized subjects in the final analysis.[8] Linear mixed models will be used to analyze the 1-100 scale satiety outcome collected across 5 SMS measurements in each phase. Energy intake and macronutrient intake will be compared using a paired t test. Subject will be considered a random effect.

We will also employ post intake sensory evaluation and measures of fullness and satisfaction as a secondary outcome.

The tertiary variables will be the standardized score from the 51-question "3 factor eating" questionnaire and the 155 item FFQ. The model will include fixed effects for the questionnaire score, visit (time points), and their interaction. Random effects will account for repeated measures within subjects.

The 51-question survey to be collected includes both true/false and Likert scale (1-5) questions. To standardize the scores we will do the following:

1. True/False Questions: We will convert responses to a numerical scale (True = 1, False = 0).
2. Likert Scale Questions: These questions are already on a numerical scale (1 to 5) and will be used as-is. IRB#: 24245 Version Date: 10/25/2024 Page 15 of 27
3. Standardization: To standardize the scales we will calculate z-scores for each question type to. This standardization method involves subtracting the mean and dividing by the standard deviation for each question.
4. Composite Score: We will then combine the standardized scores across all 51 questions by averaging them to create a single composite score for each participant for this survey.

Interaction Effects If the interaction between the questionnaire scores and visit, or visit alone is significant, we will then generate estimated marginal means and pairwise comparisons for the satiety scale outcome at each visit.

Model Variations Two different models will be considered for the outcomes: i. Unadjusted Model: This model will include only the primary explanatory variables (standardized questionnaire score, visit, and their interaction). ii. Adjusted Model: This model will adjust for additional covariates such as age, sex, and baseline health status.

Area Under the Curve (AUC) Finally, we will also apply a SAS macro for obtaining Areas Under the Curve (AUC) for the 1-100 scale across the 5 measurements during the test day. The SMS the evening prior will be used as a covariate if necessary. These AUC values will be statistically compared by the macros to assess the overall relationship between the standardized 3 factor eating questionnaire score and the FFQ on the AUC of the outcome across both visits following https://www.lexjansen.com/wuss/2004/posters/c_post_the_sas_calculations_.pdf).

Gadbury GL, Coffey CS, Allison DB. Modern statistical methods for handling missing repeated measurements in obesity trial data: beyond LOCF. Obes Rev 2003;4:175-84. https://doi.org/10.1046/j.1467-789X.2003.00109.x.

Senn SS. Cross-over Trials in Clinical Research. 2nd edition. Chichester, Eng. ; New York: Wiley; 2002.