The Old and Venerable Form of Fasting Priests and faithful who are able to do so are exhorted to observe the old and venerable form of fasting (see Black Fast below). However, since this strictness may not be suitable for most people a compensation may be made, and that is that only one full meal a day or two smaller meals that is about the same (or a little more than the full meal per day) be taken. So either one of these per day and not both as the modern day weak and pathetic fast permits. Most people should be able to do this on regular fasts. However, this fast is much harder to practice during Lent. In general, the less one eats the better, and if the above fast is too much for a person, then he should try to eat three smaller meals a day instead and skipping the full meal or eating a full meal and one smaller meal and skipping the second small meal. All those who will make use of these concessions must compensate for the good received by becoming shining examples of a Christian life and principally with works of penance, self-denial and charity (and fervent prayer).
See the: Traditional Catholic Calendar and for the Laws of fast and Abstinence, for Days of Fast and Abstinence