Fasting is a period in which purify the body and spirit. Often applied before major religious holidays, but often people and voluntarily make a fasting or purification of the body.
It is expected that during this period to feel healthier, lighter and more energetic. But it depends on how drastically apply moan and how your body is ready for such a change.
Fasting is not a diet or way to lose weight, but only the purification of the body.
See how the body organs during the most rigorous fasts: