Comparing the effect of protein quality on satiety and energy intake between egg and cereal breakfast, following a reduced calorie diet

Background: Eggs have been shown favorable satiating characteristics in breakfast from its high-quality protein, and egg breakfast enhanced weight loss in a low-calorie diet. However, limited study investigated the satiety effect of eggs when combining the high-quality protein feature and weight loss diet. In this study, we compared the Egg Breakfast (EB) containing high quality protein with Cereal Breakfast (CB) in a reduced calorie diet, to investigate the effect on satiety. A pilot study has shown inconclusive results; therefore, we expanded the sample size to investigate our hypotheses in this study. Methods: This was a two-week crossover study with 2 experiments. In each experiment, 20 sedentary women (18-44y old) who were overweight or obese (BMI 25.0-39.9) but otherwise healthy, were recruited. They visited the clinic daily to receive in random order either EB or CB each for one week and then reversed to CB or EB for another week. The two breakfasts were similar in energy density and macronutrients but differed in protein quality (mainly egg protein vs wheat protein). The two experiments were different in test days: Day 7 & 14. During the test days in Experiment 1, blood draw (to measure GLP-1, PYY, ghrelin; and glucose & insulin) and satiety questionnaire using Visual Analog Scale (VAS) were included at 6 time points (-30, 30, 60, 90, 120, and 180min), before and after the breakfast; at the last time point 240min, the last VAS was provided, followed by ad libitum lunch. Besides, ad libitum dinner was provided 4 hours after lunch. In Experiment 2, all the procedures were the same except: there were no blood draw and dinner; tempting food brownie was included in lunch. We had a pilot study with 10 samples sizes per experiment, and we combined these data for final analysis. In addition, secondary outcomes from Body Composition Questionnaire were included to measure desired weight loss and self-reported bias of height, weight and body fat percentage. Results: 20 subjects (n=10/experiment) from the pilot study were combined for analysis, resulting in 30 subjects in each experiment. Area under the curve (AUC) for each VAS factor (hunger, thirst, fullness, nausea, and the amount that could be further eaten) and blood compounds were compared between 2 breakfasts using a linear mixed effect model, adjusting for subject and visit. In experiment 1, there was no significant difference in: appetite hormones GLP-1, PYY, and ghrelin; glucose and insulin levels; subjective satiety measure from VAS; and energy intake at lunch and dinner. There was no evidence of carry-over effects. In experiment 2, EB showed significantly more fullness (p=0.038); while other factors from VAS were not significantly different. Energy intake of lunch and brownies were not different either. There was no evidence of carry-over effects. Reported body fat composition was 7.61% significantly lower than the measured value (p=2.156*10^ (-4)), but height and weight were not different. 90% of the participants intended to lose weight and their ideal weight loss ranges from 5.4kg to 34.1kg (7.13%-38.53%), which is over expected compared to the lifestyle intervention, and only comparable to bariatric surgery. Conclusions: Our study showed that high protein quality from EB induced more feeling of fullness, but did not reflect on appetite hormones and following energy intake.