Postprandial Response of Plasma Ghrelin Levels to Various Test Meals in Relation to Food Intake, Plasma Insulin, and Glucose

Ghrelin is an orexigenic gastric hormone that decreases in peripheral blood after carbohydrate-rich meals but increases after protein ingestion. In the present study plasma ghrelin was determined together with hunger and satiety ratings and with insulin and glucose concentrations after the ingestion of satiating quantities of carbohydrate-, fat-, protein-, fruit-, and vegetable-rich meals in 14 healthy subjects. Four hours later, standardized sandwiches were consumed. After carbohydrate, ghrelin decreased, whereas fat, protein, fruit, and vegetable ingestion significantly increased ghrelin levels. Considering all test meals, no significant correlation existed between changes of ghrelin levels and satiety ratings (r = 0.05; not significant), whereas a significant inverse relationship was observed between plasma ghrelin and insulin levels (r = -0.44; P < 0.001). During the second meal, sandwich consumption was significantly greater after the preceding fruit and vegetable meals, which was significantly correlated with the fourth-hour increase of ghrelin (r = 0.44; P < 0.001). In conclusion, after an overnight fast, ghrelin release depends on the ingested macronutrients and is most likely not a major regulator of acute food intake, although it is of greater importance for the recurrence of hunger and subsequent meal size.