A randomized trial to manipulate the quality instead of quantity of dietary proteins to influence the markers of satiety

Aims To test whether a breakfast including eggs (EB) containing high-quality protein decreases subsequent food intake and increases satiety-related hormones in overweight or obese adults more than a breakfast including cereal (CB) of lower protein quality, but matched for energy density and macronutrient composition. Methods Twenty healthy overweight or obese subjects were randomized to eat an EB or a CB daily under supervision for one week, followed by a crossover to the opposite breakfast week after a two-week washout period. On days 1 and 7 of each test week, a structured lunch was provided ad libitum. Food intake, hunger and satiety scores, and blood parameters were measured before and after breakfast. Outcomes were analyzed using mixed effects statistical models for repeated measures analysis of variance. Results Compared to the CB week, during the EB week, a) feeling of fullness was greater (P < 0.05) on day 1 but not on day 7; b) energy intake was not significantly lower on either day; c) right before lunch, acylated ghrelin was lower and PYY3-36 was higher on day 1 (P < 0.01 and < 0.002, respectively) but not on day 7; d) PYY3-36, but not ghrelin, showed greater rise between breakfast and lunch on days 1(P < 0.001) and 7(P < 0.01). Conclusion Despite a highly similar energy density and macronutrient composition, the higher protein quality breakfast significantly influenced fullness, ghrelin and PYY3-36. Only the effect on PYY3-36 lasted throughout the week. A next step would be to test if the benefits are pronounced and lasting, if protein quality of all meals is increased.