Effects of breakfast dietary protein source and level on satiety

Although dietary protein increases acute satiety relative to carbohydrate, the influence of protein source and level has not been clearly described. The objective of the present study was to assess acute satiety, postprandial insulin response, and post-meal behavior using different protein sources and levels. Rats were given a breakfast-like meal approximating 20% of total daily intake and containing either 35% or 20% of calories from egg white or wheat gluten. Subsequent ad-libitum chow diet intake, plasma insulin levels, and post-meal behavior were monitored. When fed a normal protein level (20%) there was no effect of protein source on intake of chow during the test period. However, the response to the higher protein diets was determined by protein source. Animals fed the 35% wheat gluten diet consumed more than the control group, while those fed the 35% egg white diet ate less than the control group. When fed at 20% of daily intake none of the diets were completely satiating as all animals consumed food during the initial period of the test period. However, it was during this period that the differences between diets were most apparent. All diets induced the behavioral satiety sequence of feeding, grooming, and resting after both breakfast and during the test period. There tended to be a lower insulin response to the higher protein diets, with the response to egg white being lower than wheat gluten. These results support the hypothesis that both protein level and source affect acute satiety in rat