Yes, the first thing is the concrete laws that God commanded us. This refers to matters of eating and drinking. It is a form, a concrete expression, of fasting and penance, which was sanctified by Our Lord Himself in the Old Testament. Our Lord also recommended this and, at times, commanded it. Therefore, the Church can command and require fasting on special days. If someone is unable to do this because of physical conditions, of course, priests or other superiors can grant a dispensation.
There is a dispensation, but not one you can decide for yourself. As members of the Catholic Church, which is hierarchical, we must obey the laws of the Church.
If you ask if there is an exemption, or simply if you don’t like fasting, you must overcome this in a spirit of obedience. Fasting is good for you physically, in fact, many doctors recommend it. It will also be beneficial when you have no serious health problems. Sometimes, if you feel hungry while performing difficult work, you can be dispensed from fasting, this is also possible.