Does ingested fat produce satiety?

Administration of fat directly into the gastrointestinal tract of rats produces a rapid and often substantial reduction of feeding behavior. This contrasts with the normal consumption of a fat meal, which produces little change in subsequent food intake. To determine whether procedural differences account for this discrepancy, we examined the satiating effect of ingested fat on food intake of rats maintained under feeding conditions similar to those employed in studies involving gastrointestinal delivery of fat (i.e., food deprivation, liquid diet). Ingestion of approximately 1.5 ml corn oil had no effect on subsequent liquid diet intake until 90 min after oil ingestion. When rats ingested oil 4 h before access to the liquid diet, to allow time for additional gastrointestinal clearance, liquid diet intake was reduced by 13% in the first 30 min of access. These findings indicate that ingested fat decreases short-term intake slightly, but only if time is allowed for postabsorptive delivery. The results question the physiological significance of the marked suppression of food intake observed in response to administration of fat directly into the gastrointestinal tract.