There is provided an apparatus for monitoring the ingestion of food and/or drink by a subject, the apparatus comprising a control unit that comprises a first obtaining module configured to obtain measurements of one or more physiological characteristics of the subject; a second obtaining module configured to obtain measurements of eddy currents generated in the body of the subject by an externally-applied magnetic field; a setting module configured to set a respective cut-off frequency for one or more filtering stages based on a respective frequency for each of said one or more physiological characteristics; a filtering module configured to filter the measurements of eddy currents using the one or more filtering stages to remove signal components due to the one or more physiological characteristics; and a processing module configured to process the filtered measurements to determine whether food and/or drink is present in the stomach of the subject.