Cannot Live on Bread Alone

Fasting has been done for religious ritualistic purposes all over the world since before recorded history.  But evidence shows it does indeed promote health and vitality.  And because man cannot live on bread alone, prayers are often recited during a fast.  Prayer and fasting go hand in hand.  The Shepard of Hermas details fast offerings in the same manner as LDS fast offerings are intended to be used but it also lays out instructions for prayer as well.
In Islam fasting is similar:
,"'O' you who believe, fasting is prescribed for you as it was prescribed for those before you so that you may achieve Taqwaa (righteousness, God-fearing)." [Surat Al-Baqarah, verse 183]
The prophet Muhammad ﷺ said, "Whoever observes the fast during the month of Ramadan, (while) believing in Allaah and seeking His rewards, will have his past sins forgiven." [Reported by Imaams Bukhaari, Muslim and others]
Fasting the month of Ramadan is one of the main pillars of Islam. It is obligatory upon every sane, healthy Muslim whose reached puberty and is not traveling during the time of fasting. As for women, they must not fast if they are menstruating or having post-childbirth bleeding.

The Essential Elements Of The Fast

There are two essentials elements for your fast to be valid and accepted. They are:

Intention

You must have the intention to fast before fajr (dawn) every night during the month of Ramadan. The intention does not need to be spoken, because in reality it is an act of the heart, which does not involve the tongue. It will be fulfilled by one's intention from the heart to fast out of obedience to Allaah ﷻ seeking His pleasure.

Abstaining from acts that nullify the Fast

The second essential element for your fast to be accepted is that you abstain from the acts that nullify the fast from dawn to sunset.

If you maintain these two essential elements during fasting, then your fast will be valid and accepted.

Six Actions That Invalidate Or Nullify The Fast

All scholars have agreed that the following acts will invalidate the fast. They are:

Intentional Eating or Drinking

If someone eats or drinks due to forgetfulness, a mistake, or coercion, then his fast is still valid and should continue to fast. If you choose to eat or drink, for any reason, then your fast will become invalid.

Intentional Vomiting

If one is overcome by the urge to vomit, and vomits unintentionally, then he should continue to fast. If someone chooses to vomit, for any reason, then his fast will become invalid.

Intentional Sexual Intercourse

If one has sexual intercourse while fasting, then he must perform kaffaarah, expiation of the sin. (Fasting continuously for sixty days or if unable then one should feed sixty poor people).

Menstrual or Childbirth Bleeding

The fast becomes invalid during menstrual or post-childbirth bleeding. Even if such bleeding begins just before sunset, the fast of that day is invalid and the day must be made up at a later time.

All the actions mentioned above are agreed upon by all scholars."
The text on Islamic fasting is found at  http://www.raleighmasjid.org/imam/fiqh-ramadan.html
 Fasting in Hinduism is more about abstaining from worldly things but there is a similar ritualistic sense as in other world religions.
Fasting in Buddhism  is a method of self-control as the idea of abstaining is also in part a matter of self-control.  And the surplus of food derived from those who fast goes to the needy who rarely get a proper meal.
In early Christianity when new followers joined the community, often there was not enough food for everyone so all fasted until there was enough for all.  If only we observed the same practice in our communities, we would not sit idle while many of our brothers and sisters go without.
There are many example in every religion of fasting and praying as a method of growing closer to God, of discovering the divine spark within.  And also of donating unneeded food to those in need.
The Bible is full of stories and verses describing fasting.
So when you fast it may be helpful to think not only of the prophets, patriarchs, apostles, Jesus and others who fasted and prayed, but thinking of anyone of faith who at any given moment are fasting along side you from every corner of the Earth and across the centuries.  And review the evidence that proves fasting cleanses the body and mind.
If you look closely you will see striking similarities in all world religions, especially in regard to fasting.  The intent, thought, even specific practices closely resemble one another.  The hearts of the faithful of every faith are in the same place as they also are in the over arching theme of every faith: love, compassion, camaradery.  Essentially to be one with yourself and those in the world around you, your neighbor, your enemy and all those you meet.
Salvation doesn't lie in good works or in checking off boxes on a list of commandments you keep; the kingdom of God is within you and once you let the kingdom reign within good works are a result of having been saved because then all commandments will be achieved and magnified.  And fasting and prayer are exceptional tools in achieving that salvation, that Christ-consciousness.