As for fasting, it’s good effects are tremendous and its end results are great. That is because it is a protection. Imaam Bukhaari and Imaam Muslim reported the hadeeth: ”Fasting is a shield.”  It is shield of protection against the hell fire in the afterlife and it is a protection against disobedience (to Allaah and His Messenger).
Fasting weakens the desires of a person; so it retrains the whims of a person and acts as barrier against the perils and forbidden things he may fall into due to engagement in enjoyment (i.e. enjoyment that may exceed the limits impose by Allaah and His Messenger). Indeed the soul may engage- due to such enjoyment- in affairs whose end results are unpraiseworthy in this worldly and the hereafter; so because of this the Prophet (sallal laahu alayhi wasallam) said: ”Paradise is surrounded by hardships and the hell fire is surrounded by all kinds of desires and passions.”
The path to paradise requires patience in order to abstain from disobedience and the path to the hell fire is surrounded by all (forbidden) desires. If a person distances himself from those forbidden desires, he/she will be safe; but if he/she engages in such forbidden desires he/she will fall into what Allaah has forbidden. This forbidden enjoyment will be one that quickly fades away, but its end results will be grief, regret and humiliation in this life and the next. It has been reported in a hadeeth narrated by Abdullaah Ibn Mas’ood (radiyallaahu anhu) that the prophet (sallal laahu alayhi wasallam) said: ”O young people! Whoever among you is able to marry, should marry, and whoever is not able to marry, is recommended to observe Sawm (fast) as fasting will diminish his sexual power.”
Therefore, the Prophet (sallal-laahu-alayhi-wasallam) made it clear that if a person is able to get married, he should hasten to do so in order to remain chaste and enables another person (i.e. wife) to remain chaste; but if he is not able, he should devote himself to this Prophetic remedy which the Noble Messenger directed him to, and that is fasting. And that is because it is a safeguard and a protection for a person against falling into disobedience. In summary: This is a Noble Prophetic guidance given by the Noble Messenger (sallal-laahu-alayhi-wasallam) to the youth-that they should get marriage if they are able to do so; but if not; they should restrain their desires through fasting.
As for the fasting of the wealthy people, it reminds them of hunger pangs; so they reflect upon the blessings Allaah has bestowed on them because they have Muslim brothers (and sisters) who suffer from hunger pangs (even) without fasting. And that is because they cannot find something (i.e. food) to do to away with extreme hunger. So this reflection becomes a drive (or motive) for them (i.e. the wealthy) to show kindness towards the poor and to spend on the destitute and needy.
[Abridged and slightly paraphrased. Source: أثر العبادات في حياة المسلمpages: 23-26]
 Bukhaari No1894 and Muslim No: 1151
Muslim No: 2822 and Bukhaari No: 6487]
 Bukhaari No: 5065