Let's be sensible about eating and fasting.
Fasting has several useful effects on our bodies and minds. 1) During a fasting period, the body begins cleaning house and immediately starts eliminating toxins long stored which is healthy (and sometimes uncomfortable). 2) Fasting also shifts and refines consciousness, which of course is powerfully useful during times of inner reflection and worship; 3) Fasting is an austerity which purifies the mind and develops will power. And finally 4) when millions of people all around the globe choose to fast together with an uplifting and spiritual intention, this seems to have real effect on the worlds we live in and on our day-to-day lives.
Now -- about eating both before and after a fast: It doesn't matter too much what you eat before a one day fast, but drink a good bit of water if your fast includes no liquids. You could actually eat nothing all day before a one day fast and still fast the next day, which would be a two day fast. (Many people do three day, seven day and 30-day fasts as regular spiritual pratices -- but almost always "with" water.) So, it doesn't really matter what you eat "before" a fast day.
However, there's a tendency to gorge one's self after the fast. This is not advised because you have arrived at an uplifted and altered state of consciousness, and stuffing yourself will bring you down into the trough of day-to-day life. It's hard not to gorge ourselves at a big break-the-fast dinner where the vibe very soon becomes eat-eat-eat! This is no big sin; it's sort of fun. But we do lose the high. However if you fast a long time (3 days or more), it's quite dangerous for your body to eat heavily as you begin to break your fast.
A common Yoga practice is to do a liquid fast one day each week or every two weeks.
Rumi says fasting will turn a crust of bread into a seven-layered dessert.