The Effects of Protein Source on Appetite Control, Satiety, and Subsequent Food Intake: A Clinical Screening Study

Primary Objective: To examine whether the consumption of preloads varying in protein quality effect subsequent meal energy and macronutrient content Secondary Objectives: To examine whether the consumption of preloads varying in protein quality effect postprandial feelings of hunger, fullness, desire to eat, prospective food consumption, and eating initiation. Exploratory Objective: To examine whether the consumption of preloads varying in protein quality effect postprandial cognitive performance.

The investigators propose the following acute, randomized crossover study to compare 5, isocaloric yogurt-based preloads containing 20, 30, or 40 g pea protein; 20 g whey protein; and an isocaloric carbohydrate (control). For 3 consecutive days/pattern, the participants will consume the respective treatment, at home, between 7-9 am, based on their habitual breakfast time. (These days are implemented to allow for the acclimation to the respective preload. Using this approach, the participant becomes familiar with the taste profile along with the practice of consuming a breakfast 'shake' so that the testing day more closely assimilates the habitual effects of the preload on appetite, satiety, and food intake.) On day 4, the participants will report to the research facility 1 h prior to their habitual breakfast time to complete each 4-h testing day. Upon arrival to the facility, each participant will become familiarized with the testing day procedures. At time -15 min, a baseline set of computerized appetite/satiety and cognitive function questionnaires will be completed. At time 0 min, the respective preload will be provided. Immediately following the first swallow of the preload, the participants will be given a questionnaire assessing the palatability. The participants will consume the preload within 10 min. Afterwards, the participants will continue to complete the questionnaires every 30 min throughout the 4-h postprandial period. In addition to these questionnaires, participants will complete a cognitive function paradigm at -30 min, +90 min, and +180 minutes in order to assess memory, executive function, attention, and reaction time. Throughout the day, the participants will also indicate if/when they would like to eat again. Regardless of their meal timing request, at 4-h post-breakfast, lunch will be provided. The participants will be given 30 min to "consume as much or as little as they wish until comfortably full." Following these procedures, the participants will be allowed to leave the facility. There will be a 3-7 day washout period between testing days.