A method is provided that includes providing a fundic impedance signal of a subject sensed during an initial calibration period using at least one implantable fundic sensor of an eating detection device. An indication is received of actual ingestion events of the subject during the initial calibration period. Using a cost function, an analysis is performed of the fundic impedance signal and the actual ingestion events. Responsively to the analysis, a threshold is set, the crossing of which by the fundic impedance signal is indicative of ingestion. The threshold is stored in a memory of the eating detection device. Other embodiments are also described.