For greater ascesis, some may choose to go without food entirely for a short period of time.
From the en.wikipedia.org
In this passage, St John of Sinai says that the primary task of the Hesychast is to engage in mental ascesis.
From the en.wikipedia.org
At 26 he made his first penetration of the far north-outwardly to search for ore in the Hudson Bay country, inwardly to search for an arctic ascesis.
From the time.com
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Asceticism: rigorous self-denial and active self-restraint
(ascetical) ascetic: pertaining to or characteristic of an ascetic or the practice of rigorous self-discipline; "ascetic practices"
(ascetical) ascetic: practicing great self-denial; "Be systematically ascetic...do...something for no other reason than that you would rather not do it"- William James; "a desert nomad's austere life"; "a spartan diet"; "a spartan existence"
Asceticism (/u0259u02C8su025Btu026Asu026Azu0259m/; from the Greek: u1F04u03C3u03BAu03B7u03C3u03B9u03C2 u00E1skesis, "exercise" or "training") is a lifestyle characterized by abstinence from worldly pleasures, often for the purpose of pursuing spiritual goals...
Self-discipline
It is so called man's effort as well as the method he uses to pass through the three stages of the spiritual life: purification of heart, illumination of the nous and theosis. Since this is achieved through the commandments of Christ, ascesis is man's struggle to keep the commandments of Christ. ...
The practice of penance, mortification, and self-denial to promote greater self-mastery and to foster the way of perfection by embracing the way of the cross.