According to an aspect, there is provided a method of monitoring a subject, the method comprising obtaining measurements of a parameter relating to one or more volatile organic compounds, VOCs, in one or more outputs of the subject over time, wherein the one or more VOCs are associated with the food or produced while the food is metabolised or digested by the subject and processing the measurements to determine an amount and/or type of food ingested by the subject and/or a health status of the subject.
