Dear maxdouglas402–
(I am not Catholic, and I don’t know if the Catholic Church has specific recommendations, but these are general recommendations based on my own fasts.)
Before a fast, I would recommend eating as healthy as possible–lots of fruits and veggies, and limit the amount of junk food you eat. Afterward, you might want to start back with only juices at first, to avoid too much of a shock to your digestive system; then work your way up to easily digested, juicy fruits (melons, grapes, etc.), then veggies, then starches/grains, dairy, and meat (if you eat them).
Of course this would depend on how long your fast is–the longer the fast, the slower you should ease back into eating. If you’ve only been fasting for a day or two, then you might only need a day to acclimate back to “real food.” If it’s a week or longer, you might want to only do juices/fruits the first day after the fast, add veggies the 2nd day, and wait a few days to add foods that are harder to digest.
Jala