Background: Consistent data from acute, single preload studies demonstrate improvements in perceived appetite and satiety following the consumption of high-protein preloads compared to normal protein preloads. However, it is currently unclear as to whether protein quality (i.e., protein source) or the use of appetite questionnaires influences these outcomes. Objective: To examine whether the consumption of protein preloads (egg white isolate, whey isolate, micellar casein, and instant egg white) differentially modulate postprandial hunger, fullness, desire to eat, prospective food consumption, eating initiation, and subsequent food intake; and if the use of appetite questionnaires to assess perceived appetite and satiety affect subsequent energy intake. Methods: Twelve young adults (age: 22±1 y; BMI: 22.1±0.9 kg/m2) reported to the research facility between 7 - 9 am to complete each 4-h testing day. A set of questionnaires assessing perceived hunger, fullness, desire to eat, prospective food consumption were completed followed by the consumption of the 130 kcal beverage preloads, varying in protein source. A water preload was also included as a control. The same set of questionnaires along with the assessment of whether they would like to eat again were completed every 30 min throughout the 4-h postprandial period. On a separate day, all twelve young adults also completed a similar testing day except were not given questionnaires throughout the 4-h postprandial period. After the 4-h, the participants were given an ad libitum pasta meal to consume until 'comfortably full.' Results: The consumption of the protein preloads improved hunger, fullness, desire to eat, prospective food consumption and delayed the request to eat again vs. the control (water); however, no differences in appetite and satiety outcomes were observed between protein sources. No differences in energy content at the lunch meal were observed between any preloads. The use of questionnaires did not change energy consumed at the lunch meal. Conclusions: When comparing high-quality animal-based proteins consumed as a beverage preload, relatively no differences in markers of appetite control and satiety were detected, suggesting that protein quality has little impact on these outcomes when consuming 30g of protein. In addition, the use of questionnaires assessing perceived appetite and satiety do not impact subsequent energy intake.

the following acute, randomized crossover study will be completed in 12 healthy adults (age 18-35y; BMI: 18-29.9 kg/m2) to compare 135 kcal protein beverages consumed at breakfast containing 30 g of protein from whey isolate (WY), casein (CS), egg white isolate (EWI), egg white protein concentrate (EWP), or a 0 kcal water beverage - which serves as the control (CON). Note: the W beverage will be consumed on 2 different days; these days only differ by the postprandial outcomes completed (see below).

The participants will report to the research facility between 7 - 9 am to complete each 4-h testing day. Prior to testing, the participants will be provided with a standardized dinner to consume, at home, between 5-7 pm the night before each 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 questionnaires will be completed. At time 0 min, one of the breakfast beverages will be provided. Immediately following the first swallow of the breakfast shakes, the participants will be given a questionnaire assessing the palatability of each shake. The participants will consume the beverage within 20 min. For 5 of the 6 days, a set of questionnaires will be completed every 30 min throughout the 4-h postprandial period. For one of the W days, no questionnaires will be completed. After the 4-h, the participants will be given an ad libitum pasta meal to assess energy intake. For the lunch meal, the participants will be given 30 min to "consume as much or as little as possible until comfortably full." Following these procedures, the participants will be allowed to leave the facility. The next day, a dietary recall will be performed to assess daily energy intake following the consumption of the previous day's breakfast beverage.

Inclusion Criteria:

1. healthy
2. ages 18-35 years old
3. normal weight to overweight (BMI: 18.5-29.9 kg/m2)
4. no metabolic, psychological, or neurological diseases/conditions
5. weight stable (no weight loss/gain within the past 6 mo)
6. not currently on a weight loss or other special diet (in the past 6 mo)
7. not a vegetarian
8. not pregnant
9. non-smoker

Exclusion Criteria:

1. Unhealthy
2. ages <18 or >35 years old
3. underweight or obese (BMI: <18.5 or >29.9 kg/m2)
4. metabolic, psychological, or neurological diseases/conditions
5. not weight stable (weight loss/gain within the past 6 mo)
6. Currently on a weight loss or other special diet (in the past 6 mo)
7. A vegetarian; 8) pregnant; and 9) smoker