Contributed by: Rabbi Haim Shaul
Who has to fast?
Both men and women have an obligation to fast on the 13th of Adar. The fast begins early in the morning and ends with the reading of the Megillah, after the sun has set.
Women who are pregnant or nursing their children do not have to fast the Fast of Esther. Even during the first 40 days of pregnancy, where the fetus is not fully developed, a woman who has trouble fasting is allowed to eat.
One who is sick, even not seriously, does not have to fast. If someone feels particularly weak, especially the elderly, do not have to push themselves to fast.
For the above-mentioned, it is not allowed for them to be more strict and push themselves to fast. This is not the point of the fast. The point of the fast is to remember and feel the suffering that the Jews felt at that time. One cannot do that when they are sick, or when fasting may cause potential birth complications.
A "Chatan", during the days of shevah berachot (the seven days following his wedding), does not have to fast. Similarly, the father of a new born boy, the "sandak", and the "mohel", are all exempt form fasting if the Fast of Esther falls on the same day as the Brit Milah.
Everyone else must attempt to fast and not separate themselves physically or spiritually from Kilal Yisrael.
One should not have a full meal with bread until the megilah is heard from kosher megilah scroll. If one is praying in a later minyan, it is permissible to eat after the fast technically ends, but no bread should be eaten (indicating that one is having a "meal").