From the Greek "askesis," which referred to the rigorous training process undergone by athletes to prepare for athletic games. In particular, this athletic training emphasised certain restrictions, requiring a degree of self-denial. In early Christian theology, this practice translated to avoidance of the fleshly desires of the pagan world, including food, drink, sexual activity, wealth, and power. The intent of this self-deprivation was to focus the energy of the individual on intellectual and spiritual growth.

St. Antony tortured by demons (from S. Baring-Gould, Lives of the Saints [London and New York, 1898])

Over the years, devoted ascetics have frequently locked themselves away from the world in order to pursue their lifestyles of self-denial more successfully. In removing the sources of their temptations, it was easier to focus their energies on denial of the flesh and growth of the spirit. A common destination for many early hermits was the desert (which covered quite a large portion of the world during the time of early Christianity), where in caves or cells, they would meditate on God while forgetting the evils of society.

One of the earliest recorded hermits was St. Antony (pictured above), who ventured into the desert after the death of his parents (c. 250-356). As a young Christian, Antony felt the need to remove himself from the tainted society that surrounded him and offered him a lavish lifestyle (as his parents were quite wealthy). St. Antony's lifestyle of eremitic deprivation soon became extremely famousamongst the newly formed Christian people, and thus arose a great desire to emulate this holy man and his lifestyle of asceticism.

More About St. Antony from The Columbia Encyclopedia

A later form of the eremitic lifestyle was displayed by anchorites, who lived in one-room cells connected to a church by a small window through which food and supplies could be passed. Julian of Norwich was one of the most famous anchorites, whose work, Revelations of Divine Love (c. 1393) outlined the relationship between God and man. Her physical solitude allowed her to strengthen her spiritual wisdom and receive visions from God regarding the nature of his love for humankind.

More information about Julian of Norwich can be found at luminarium.org

Asceticism was (and still is) a large factor in the institution of monasticism. In a monastic lifestyle, denial of the pleasures of the world is considered to be a key factor in attaining perfection. The primary focus of this self-denial was celibacy. It was common belief that in order to lead a truely Christ-like life, one had to avoid all temptations (sexual temptations being the most dangerous). Those ascetics who remained unmarried were viewed as a higher class by the church than those who did marry.

Despite the fact that celibacy has been considered to be quite possibly the highest form of asceticism, fasting (partial or temporary abstinence from food) has been the most commonly practiced form. It has been long believed in Christian theology (as well as in other religions) that fasting provides an individual with the ability to strengthen the spiritual body as it deprives the physical body. The practice of Lent is an emulation of the 40 day fast undergone by Christ prior to his crucifiction. Thus, devoted Christians intending to engage in what is known as imitatio Christi (imitation of Christ) will observe this fast by giving up what they consider to be an important pleasure for the 40 day observance.