As I was considering more and more Advent spiritual disciplines and practices throughout the Holy History of the Christian Church I began to ruminate on fasting.
One thing I learned quickly in the Roman Catholic Church was that fasting did not simply mean abstaining from all food for a whole day. As a young Baptist, this is what I was taught fasting consisted of, though I never practiced it or was encouraged avidly to practice it until I reached Evangelical Bible School. We tended more towards Luther’s mild and vague admonition that fasting was of ‘some profit’ as he interpretted St. Paul’s words. Fasting can consist of avoiding certain foods, or food types, or simply by cutting out specific meals and can be for periods shorter than 24 hours.
In the history of the Church the importance of asceticism can hardly be overstated. Irish monks became vegetarians, Egyptian desert fathers lived on pillars or in caves, Blessed Julian of Norwich had herself sealed up in a church wall, and some poor sisters in the middle ages survived on nothing but pus and the Eucharist. The Roman Church has since the Second Vatican Council become quite lax on issues of fasting and abstinence, and in Canada the only obligatory fast days (when last I looked) were Ash Wednesday and Good Friday (no meat and 1 and a half meals I believe were the proscriptions). The Lutheran Church is probably the worst in terms of asceticism with it’s almost total abolition of religious orders, and removal of obligatory fasts. The general stereotype that the Calvinists were more austere and disciplined is, for the most part, accurate.
The Eastern Church is immensely rooted in asceticism almost to the point of worry to some of us lax Westerners. They fast twice a week from all meat and dairy (Wednesday for Christ’s betrayal by Judas, and Friday for Christ’s death). Throughout Advent the Orthodox keep this Fast as well, which would be intense. This is one of the many stumbling blocks I have with the Greeks where I need to learn from their Sacred Tradition, though my Pentecostal friends admire their fasting, since they too see the importance of asceticism. 
A noteworthy criticism offered during the Reformation and the Early Modern Period however was that far from pure devotion, the Church calendar made fasts during times when food was scarce already. This reminds me of a line from Ray Raphael’s History of the American Revolution where a group of starving soldiers (Reformed Protestants) joke about keeping a Lenten fast stricter than any Roman Catholic (because they had no food). Likewise, my friend who was curious about the Orthodox Church, met a Greek friend whose family could cook up marvellous feasts during Advent and Lent which carefully avoided the forbidden ingredients, while still being quite decadent. The same could be said of Italian Roman Catholics I know who eat Lobster and Crab on fridays in Lent under the pretense of fasting from meat. For all these reasons, Lutherans and other Protestants have focused on the intent and the heart of the matter rather than the external practice, though at the cost of letting abuse rule out use.
In my own life, the little fasting I’ve done has helped immensely in my prayer life, and at times I feel so full of food that I actually think it’s more difficult to hear God. Having grown up in a fairly iconoclastic and anti-Traditional faith, I’ve always been astonished by the connections Christians wisely made between religion and the most basic of things – like food. Abstinence from certain foods has also been helpful in making me think of Christ when I plan on indulging, and realizing what a fat slob I can be. Hopefully Advent will provide another opportunity to make some serious devotions and fasts, always with the thought in mind that to become puffed up or proud of spiritual disciplines or accomplishments is worse than to do none in the first place, and that the last lesson of the Law is that it cannot be fulfilled. Thank God for Christ who fasted in ways I could not, on my behalf.