Plasma levels of the orexigenic hormone ghrelin are suppressed by meals with an efficacy dependent on their macronutrient composition. We hypothesized that heterogeneity in osmolarity among macronutrient classes contributes to these differences. In three studies, the impact of small-intestinal hyperosmolarity was examined in Sprague-Dawley rats. In Study 1, isotonic, 2.5x and 5x hypertonic solutions of several agents with diverse absorption and metabolism properties were infused duodenally at physiologic rates (3 ml/10 min). Jugular-vein blood was sampled before and at 30, 60, 90, 120, 180, 240 and 300 minutes after infusion. Plasma ghrelin was suppressed dose-dependently and most strongly by glucose. Hyperosmolar infusions of lactulose, which transits the small intestine unabsorbed, and 3-O-methylglucose (3-O-MG), which is absorbed like glucose but remains unmetabolized, also suppressed ghrelin. Glucose, but not lactulose or 3-O-MG infusions increased plasma insulin. In Study 2, intestinal infusions of hyperosmolar NaCl suppressed ghrelin, a response that was not attenuated by co-infusion with the neural blocker lidocaine. In Study 3, we re-confirmed that the low-osmolar lipid emulsion Intralipid suppresses ghrelin more weakly than isocaloric (but hypertonic) glucose. Importantly, raising Intralipid's osmolarity to that of the glucose solution by non-absorbable lactulose supplementation enhanced ghrelin suppression to that seen after glucose. Hyperosmolar ghrelin occurred particularly during the initial 3 post-infusion hours. We conclude that small-intestinal hyperosmolarity: (a) is sufficient to suppress ghrelin; (b) may combine with other post-prandial mechanisms to suppress ghrelin; (c) might contribute to altered ghrelin regulation after gastric bypass surgery; and (d) may inform dietary modifications for metabolic health.