Does higher protein quality breakfast reduce energy intake when following a weight loss diet plan?

Eggs are superior protein quality to those of plants. An egg breakfast (EB) matched for energy density and weight to a bagel breakfast (BB) increases satiety and leads to greater weight in a reduced energy setting. Matching EB and plant based protein cereal breakfast (CB) for macronutrient composition, weight, and energy but not quality of protein, results in transient reduction of hunger markers and increases those of satiety. Outcomes of superior quality EB in weight loss diet setting remain unknown. We undertook a preliminary pilot study to assess feasibility of higher quality EB in restricted energy weight loss setting. Methods: 20 women (BMI ≥ 25) were assigned to 1 of 2 experiments and randomized to consume an EB or CB for one week while following a weight loss diet, and then reversed to receive the opposite breakfast for an additional week. Energy intake (EI) at buffet lunch and dinner, anthropometrics, blood, and subjective hunger and satiety scores were measured. Appetite hormones and blood chemicals, including PYY3-36, ghrelin, GLP-1, glucose, and insulin, were assessed. Using linear mixed effects models, treatment effects and potential time and carryover effects were assessed. VAS measures used to assess hunger and satiety scores, as well as blood data, were converted into area-under-the-curve (AUC). Results: Across experiments and variables, EB produced no statistically significant effects compared to CB, although data were suggestive. In experiment 1, EI was increased at lunch (+29 kcal, p=0.581), decreased at dinner (-86 kcal, p=0.083) and lower for total EI (-57 kcal, p=0.45) for EB compared to CB. Experiment 2 produced similar outcomes of EB at lunch (-25 kcal, p=0.75) and slightly reduced consumption of highly palatable foods (-14 kcal, p=0.681). VAS were suggestive for lower hunger, increased satiety, and inability to eat more for EB compared to CB across experiments. There was no statistically significant effect of EB on blood appetite hormones or blood chemicals up to 120 minutes after ingestion despite acute and intriguing effects on ghrelin, PYY3-36, insulin and glucose. All results were adjusted for day effects and no significant carryover effects were observed. Conclusions: Even though there were no statistically significant observations for EI or markers of satiety between experiments, EB did produce acute results that are suggestive for the time being. A greater sample size and a longer term study will provide clarification.