fasting gives the individual a real taste of hunger and thirst which helps him to realize the experience of the poor. this experience should instill a desire to want to help those who are less fortunate by sharing food and wealth with them.
it is required that the individual give up not only food, drink and sexual relations, but also that he restrain from all forms of lying (e.g. backbiting, slander, etc.). this is confirmed by the prophet's (peace be upon him) statement, "allah has no need for the hunger and the thirst of the person who does not restrain from telling lies and acting on them even while observing the fast."
he also said, "when one of you is fasting, he should abstain from indecent acts and unnecessary talk, and if someone begins an obscene conversation or tries to pick an argument, he should simply tell him, ‘i am fasting'."
so, if one observes the fast according to the above principles, it should improve his moral character, making him more truthful and more careful about what he says and does.
it has also been noted by medical experts that fasting improves the physical health in numerous ways. for example, during the fast the body uses up stored cholesterol (fats) which are often deposited in the blood system, as well as in other fatty areas of the body. thus, it helps to keep the body firm and minimizes the danger of heart attacks.
fasting trains the individual for jihad (fighting in the way of allah) by giving him a good course in self-control. during war the desires of the stomach and the private parts often lead soldiers of war to either commit excesses or to unnecessarily expose themselves to danger.