A system for determining reference signatures for use in assisting identification of a body state in a biological subject, the system including at least one processing device that obtains reference data for each of a plurality of reference individuals, the reference data including at least one reference impedance indicator obtained by performing at least one impedance measurement on the reference individual, a body state indication indicative of any body states associated with the reference individual and characteristic data indicative of one or more physical characteristics of the reference individual and analyses the reference data to establish one or more reference signatures, each reference signature being indicative of at least one reference impedance indicator associated with a respective body state for respective physical characteristics.