All I write here is out of my own limited understanding of the Baha'i fast and why Baha'is do it.
From the 2nd until the 20th of March Baha'is around the world observe the law of fasting. This constitutes of no food or drink for usually 12 hours which begins at sunrise and end at sunset -basically you cannot eat or drink while there is daylight.
Knowing only this much about the Baha'i fast may seem pretty difficult or even scary to some people to attempt to do but Baha'u'llah is so Generous and Bountiful that there are several instances when people are not obliged to fast. Some of these are: pregnant women or women who are breastfeeding or have their period, those who are ill, those who are under 15 years of age - which in the Faith is the age of maturity-, those over 70, those individuals who perform daily intense physical work, among others.
The purpose of the Baha'i fast is to remind us of the important thing in life. That is, the spiritual things and the remembrance of God. To me, it gives each individual extra time (much extra time if you really calculate how many hours of our day are consumed in the making and eating of food!) to think about our lives and make the appropriate changes before the coming of the new year (Baha'i new year -Naw Ruz- is celebrated on the 21st of March). It also helps me think about the Manifestations of God that have come and will come in the future; how much they have suffered in hands of us insignificant and ignorant human beings. They have suffered enourmously both physically and emotionally for the sole reason of wanting to make the world a better place and letting humanity know the purpose of our existence today. When I think of this during the fast, I realize that fasting is a very small way to show love and detachment to those Blessed Souls who have given us so much.
Besides having a spiritual meaning, studies have shown that fasting is also good for you. Some of these benefits are: letting the digestive system rest and restore itself; it forces the body get energy from those stored fats we don't need; and the reduction of the body's core temperature due to the slow down of metabolism.
All spiritual laws are give to us to protect us and get us to benefit therefrom. We only need to look deeper and find the spiritual reasons for them and surprise! we might just find social, moral and physical benefits hidden within these laws as bounties.The Gem ring[/caption]
The following are words of 'Abdu'l Bahá that reminds us why we fast and how fasting has been a religious tradition for thousands of years...
"The Divine wisdom in fasting is manifold. Among them is this: As during those days [i.e. the period of fasting which the followers afterward, observe] the Manifestation of the Sun of Reality, through Divine inspiration, is engaged in the descent [revealing] of Verses, the instituting of Divine Law and the arrangement of teachings, through excessive occupation and intense attraction there remains no condition or time for eating and drinking. For example, when his holiness Moses went to Mount Tur (Sinai) and there engaged in instituting the Law of God, he fasted forty days. For the purpose of awakening and admonishing the people of Israel, fasting was enjoined upon them.
Likewise, his holiness Christ, in the beginning of instituting the Spiritual Law, the systematizing of the teachings and the arrangement of counsels, for forty days abstained from eating and drinking. In the beginning the disciples and Christians fasted. Later the assemblages of the chief Christians changed fasting into lenten observances.
Likewise the Qur'án having descended in the month Ramadan, fasting during that month became a duty.
In like manner his holiness the Supreme [the Báb], in the beginning of the Manifestation, through the excessive effect of descending Verses, passed days in which his nourishment was reduced to tea only.
Likewise, the Blessed Beauty [Bahá'u'lláh], when busy with instituting the Divine Teachings and during the days when the Verses [the Word of God] descended continuously, through the great effect of the Verses and the throbbing of the heart, took no food except the least amount.
The purpose is this: In order to follow the Divine Manifestations and for the purpose of admonition and the commemoration of their state, it became incumbent upon the people to fast during those days. For every sincere soul who has a beloved longs to experience that state in which his beloved is. If his beloved is in a state of sorrow, he desires sorrow; if in a state of joy, he desires joy; if in a state of rest, he desires rest; if in a state of trouble, he desires trouble.
Now, since in this Millennial Day, his holiness the Supreme [the Báb] fasted many days, and the Blessed Beauty [Bahá'u'lláh] took but little food or drink, it becomes necessary that the friends should follow that example. For thus saith He in the Tablet of Visitation: "They, the believers, have followed that which they were commanded, for love of Thee."
This is one wisdom of the wisdoms of fasting.
The second wisdom is this: Fasting is the cause of awakening man. The heart becomes tender and the spirituality of man increases. This is produced by the fact that man's thoughts will be confined to the commemoration of God, and through this awakening and stimulation surely ideal advancements follow.
Third wisdom: Fasting is of two kinds, material and spiritual. The material fasting is abstaining from food or drink, that is, from the appetites of the body. But spiritual, idea: fasting is this, that man abstain from selfish passions, from negligence and from satanic animal traits. Therefore, material fasting is a token of the spiritual fasting. That is: "O God! as 1 am fasting from the appetites of the body and not occupied with eating and drinking, even so purify and make holy my heart and my life from aught else save Thy Love, and protect and preserve my soul from self-passions and animal traits. Thus may the spirit associate with the Fragrances of Holiness and fast from everything else save Thy mention."
The divine wisdom in fasting - From table talks by 'Abdu'l-Bahá, by Mrs Corinne True. (SOW - Star of the West - 3 IV:18, 7 February 1914; page 305)