“ Section 3 It is forbidden for one to carry out their needs or travel until they pray morning prayer. (There are those who are lenient and rule that after one says some of Berachot which is before Baruch she'amar (one can fulfill their needs) ...and it is good to be strict on this issue) . One should not eat nor drink before one prays, whether it is a weekday, Shabbas or Yom Tov.
It is permitted for a sick person to eat or drink.
Section 4 One who is hungry or thirsty is considered like a sick person. ”