What the Church actually requires, and what it is for.
On Ash Wednesday and Good Friday, those between eighteen and fifty nine fast: one full meal and two smaller ones that together do not equal a full meal, and nothing between meals.
On the same two days, and every Friday of Lent, those fourteen and older abstain from meat.
The Eucharistic fast is one hour from food and drink other than water and medicine before Communion.
Fasting is not dieting and it is not endurance sport. It puts a small, honest hunger in the day so the appetite stops being the thing that gives orders, and it frees money and attention for someone else.
The Lenten fast was once far more severe and far longer, closer to what the Eastern churches still keep. The Western obligation was reduced repeatedly over the last two centuries.
The point of the reduction was never to end fasting but to move it from a minimum enforced by law to a practice freely deepened. Most Catholics received only the reduction.
The two days of fasting and the days of abstinence are obligations for those of age and in health. Anyone with an eating disorder, a medical condition, a pregnancy, or hard physical work is excused, and should substitute another penance rather than push through.