What is fasting?
Usually it refers to giving up food for a certain amount of time to spiritually prepare yourself. (The word can also be used to mean giving up something else.)
Many different religions do this. Muslims fast during the month of Ramadan, some Christians fast during Lent, and Jews have a few fasts during the year.
Some ill-advised people fast just to lose weight. This is not a recommended (or even effective) method of weight-loss. Rather, give up junk food and sweetened drinks, and eat not-large portions of healthy foods. If your weight doesn't change, see a dietician.
Fasting represents ceasing to take in further information for the time being and to concentrate solely on using the knowledge you have. In the universal language of mind, food represents knowledge. Just like food, we need time to assimilate what we take in in the way of information. The thought process mirrors the digestive system.
Fasting is the Fourth Pillar (Sawm), and means abstaining from things which break the fast, such as food, drink and intercourse, from sunrise until sunset, with the intention of fasting. The relationship of patience to faith is like that of the head to the body. Allaah has enjoined upon this ummah fasting for one month of the year, in order to draw closer to Allaah, to avoid that which Allaah has forbidden, to get used to being patient, to bring the nafs (self) under control, to compete in generosity and to demonstrate co-operation and mutual compassion. Allaah says (interpretation of the meaning): "O you who believe! Observing As-Sawm (the fasting) is prescribed for you as it was prescribed for those before you, that you may become Al-Muttaqoon (the pious)"[al-Baqarah 2:183] The month of Ramadaan is a great month, in which Allaah revealed the Qur'aan. The reward for good deeds, acts of charity and acts of worship are multiplied in this month. In it is Laylat al-Qadr, which is better than a thousand months. The gates of heaven are opened and the gates of Hell are shut, and the shayaateen (devils) are tied up. Allaah has made fasting the month of Ramadaan obligatory upon every sane, adult Muslim, male and female alike, as He says (interpretation of the meaning): "The month of Ramadaan in which was revealed the Qur'aan, a guidance for mankind and clear proofs for the guidance and the criterion (between right and wrong). So whoever of you sights (the crescent on the first night of) the month (of Ramadaan i.e. is present at his home), he must observe Sawm (fasts) that month, and whoever is ill or on a journey, the same number [of days which one did not observe Sawm (fasts) must be made up] from other days. Allaah intends for you ease, and He does not want to make things difficult for you. (He wants that you) must complete the same number (of days), and that you must magnify Allaah [i.e. to say Takbeer (Allaahu Akbar: Allaah is the Most Great)] for having guided you so that you may be grateful to Him" [al-Baqarah 2:185] There is a great reward with Allaah for fasting. The Prophet (peace and blessings of Allaah be upon him) said: "Every action of the son of Adam is multiplied, each good deed receiving a tenfold to seven hundredfold reward. Allaah said, 'Except for fasting, for it is done for Me and I will give a reward for it, for he gives up his desire and food for My sake.'"
Fasting is a ritual in which people do not eat for a certain interval of time. Traditionally one should not consume food items having salt in it, but many people have salt containing food and still say they are fasting. A few even do not drink water during fasting. Muslims observe 'roza' (fasting) for 30 consecutive days (from morning to evening)in which they do not cosume food or water (and even they can't take in their saliva to satisfy their thirst).