For having eaten too much in the past, a person would eat less than allowed. Some Christians think that the demons can find ways to stir up the emotions, particularly to make fantasies arise in the sleeping and waking mind upon which emotions and desires follow. Thus the imagination and the body become a battle ground for conflict with the demons and demonstrating fidelity to God. This asceticism can be extreme, as the Christian tries to carry the battle against the forces opposing him and to secure himself in obedience to God. With experience of monks, there is a tendency to moderate this asceticism so that it can be practiced for many years.
Third possibility is relation to society.
The body is a means of symbolizing the stance which the person takes toward society and of actually mediating that stance. The ascetic will reject and contradict things which the society finds important. Virginity means that the person breaks ties to the continuing family because it refuses to produce the next generation and thus to extend the family in time. It also symbolizes the separation of the person from the earthly society and a placing of hope and trust in a future life. Finally, it can open the person to voluntary forms of association based on common faith rather than common blood.