Background: Ghrelin plays an important role in the regulation of food intake. Little is known about how ghrelin concentrations are modified by dietary factors. Objective: We examined the effects of both amount and type of carbohydrate on ghrelin concentrations and all correlations among the variables ghrelin, glucose, insulin, leptin, and all 4 subjective measures of appetite. Design: Twenty healthy nonobese men were studied in a double-blind, randomized, crossover design. Subjective measures of appetite and concentrations of ghrelin, glucose, insulin, and leptin were frequently assessed for 4 h after liquid breakfast meals differing in energy content and carbohydrate structure-ie, water, low-calorie (LC) meal, high-calorie simple carbohydrate (HC-SC) meal, and high-calorie complex carbohydrate (HC-CC) meal. Results: Ghrelin concentrations decreased after the HC-SC breakfast by 41%, after the HC-CC breakfast by 33%, and after the LC breakfast by 24%. No significant differences in ghrelin concentration among the 3 breakfasts were observed until 120 min. Ghrelin concentrations were correlated with subjective measures of hunger (r = 0.51) and fullness (r = -0.44). The percentage decrease in ghrelin between 0 and 30 min was inversely correlated with the percentage increases in insulin (r = -0.76) and glucose (r= -0.79) but not with changes in leptin (r = 0.10). The percentage changes in ghrelin concentrations between 30 and 180 min were correlated with the percentage changes in insulin (r= -0.53) and leptin (r= -0.47) but not with changes in glucose (r = 0.22). Conclusion: The results support the hypothesis that ghrelin requires postgastric feedback, which may be regulated through insulin. © 2005 American Society for Clinical Nutrition.