RC. Enhancement of intragastric acid stability of a fat emulsion meal delays gastric emptying and increases cholecystokinin release and gallbladder contraction. Am J Physiol Gastrointest Liver Physiol 292: G1607-G1613, 2007. First published March 1, 2007; doi:10.1152/ajpgi.00452.2006.-Preprocessed fatty foods often contain calories added as a fat emulsion stabilized by emulsifiers. Emulsion stability in the acidic gastric environment can readily be manipulated by altering emulsifier chemistry. We tested the hypothesis that it would be possible to control gastric emptying, CCK release, and satiety by varying intragastric fat emulsion stability. Nine healthy volunteers received a test meal on two occasions, comprising a 500-ml 15% oil emulsion with 2.5% of one of two emulsifiers that produced emulsions that were either stable (meal A) or unstable (meal B) in the acid gastric environment. Gastric emptying and gallbladder volume changes were assessed by MRI. CCK plasma levels were measured and satiety scores were recorded. Meal B layered rapidly owing to fat emulsion breakdown. The gastric half-emptying time of the aqueous phase was faster for meal B (72 Ϯ 13 min) than for meal A (171 Ϯ 35 min, P Ͻ 0.008). Meal A released more CCK than meal B (integrated areas, respectively 1,095 Ϯ 244 and 531 Ϯ 111 pmol ⅐ min ⅐ l Ϫ1 , P Ͻ 0.02), induced a greater gallbladder contraction (P Ͻ 0.02), and decreased postprandial appetite (P Ͻ 0.05), although no significant differences were observed in fullness and hunger. We conclude that acid-stable emulsions delayed gastric emptying and increased postprandial CCK levels and gallbladder contraction, whereas acid-instability led to rapid layering of fat in the gastric lumen with accelerated gastric emptying, lower CCK levels, and reduced gallbladder contraction. Manipulation of the acid stability of fat emulsion added to preprocessed foods could maximize satiety signaling and, in turn, help to reduce overconsumption of calories. gastric emptying; lipid; magnetic resonance imaging CONSUMPTION OF PREPROCESSED foods high in added fat is steadily increasing in the developed countries. Fatty foods have high energy density and palatability but exert a relatively weak effect on satiation (compared calorie per calorie with protein and carbohydrate loads), which may encourage calorie overconsumption (5). This, in turn, may be one important factor contributing to the current epidemic of obesity in the Western population (38). Weight gain management rightly focuses on a healthy balanced diet, sensible portion sizes, and exercise. However, it would be desirable also to be able to maximize the satiating properties of fatty meals themselves. This could help to reduce postprandial hunger and, in turn, snacking, and it could also lead to improved design of slimming products.Manipulating the sense of satiety derived from a fatty meal requires knowledge of the various interactions between the gut and the brain (2,22,40). One of the main satiety mechanisms triggered by ingestion of fat is the release of...