Below are listed answers to frequently asked questions regarding fasting requirements for those who, for a serious reason, must abstain from fasting.
One who genuinely cannot fast due to a grave risk to health may request a dispensation from a priest, who may suggest that the individual substitute another act of penance instead, although this is at the discretion of the priest. However, if no priest is available, the faithful are not required to observe any fasting or abstinence laws that they know would be injurious to their health. For, after all, each of the faithful are duty-bound to safeguard the safety of the Temple of the Holy Ghost which is his own physical body.
Examples of health reasons that would exempt one from fasting. This list is non-exhaustive: hypoglycemia, a thyroid condition, diabetes or prediabetes, anorexia or any other nervous disorder, et cetera.
"Those not bound to fast may eat meat as often as they wish, except on days of complete abstinence (when it may not be eaten at all), and on days of partial abstinence (when it may be eaten only as the principal meal). When a person's health or ability to work would be seriously affected by fasting or abstaining, the law does not oblige. Where doubt arises concerning fast or abstinence, a parish priest or confessor should be consulted.
"In granting these concessions the bishops urged the faithful:
to attend daily Mass during the period of fast and abstinence;
to receive Holy Communion often;
to take part more frequently in exercises of piety;
to give generously to works of religion and charity;
to perform acts of kindness toward the sick, the aged and the poor;
to practice voluntary self-denial;
to pray more fervently, particularly for the intentions of the Holy Father.*" (*who we hope will soon emerge from his long exile and obscurity)
Quotation excerpted from Baltimore Catechism No. 3., The Text of the Official Revised Edition 1949, Rev. Francis J. Connell, C.SS.R, S.T.D., p. xiv
Pregnant and nursing mothers are dispensed automatically from fasting regulations.
Catholics under the age of 21 and over the age of 59 are not strictly bound to fast. A person over the age of 59 may choose to fast, but it is not required.