Food and drink in the Bible represent the desire for good and the understanding of what is true, which nourish and delight us spiritually the same way food and drink nourish and delight our bodies. There is some crossover between the two -- food and drink -- but in general food relates to the desire and delight of being good, and drink relates to the understanding and delight in what is true. To be hungry, then, indicates that there is a lack of desire for what is good, a lack of delight in the idea of being good, and a lack of energy and commitment to do what is good. Sometimes that comes hand-in-hand with a lack of understanding what is true, and a lack of delight in truth. This actually makes a lot of sense, if you consider how difficult it is to be cheerful, patient and tolerant when you're hungry. A famine, obviously, would represent a complete loss of desire for good and delight in good over a long period of time, to the point of threatening spiritual death.

'To hunger,' as mentioned in Isaiah 8:21, signifies to desire knowledge.