The passion of gluttony is the desire for the pleasure that comes from eating.
St Dorotheos distinguishes two types of gluttony: the gluttony that wants to fill the stomach and the gluttony that, while it may not want to fill the stomach, wants to have very tasty food.
The first leads to fat monks; the second, to gourmet monks.
St Silouan the Athonite remarks, according to his disciple, Fr Sophrony (Sakharov), that the measure of eating too much is whether after eating, our memory of God is disturbed. If someone is praying the Jesus Prayer twenty-four hours a day, this is easy to gauge.
Although the early fathers emphasize the connection between gluttony and fornication, later writers also emphasize that overeating clouds the mind, that fasting assists the mind to engage both in mental prayer (the Jesus Prayer prayed silently) and in mental ascesis (the purification of the soul through repelling tempting thoughts).
However, St Maximos the Confessor, and those following him, teach us that we must subordinate our bodily ascesis to our mental ascesis, concentrating on mental ascesis. An excessive bodily ascesis is quite dangerous. Here we must have sound guidance and not follow our own will.