In Orthodoxy, we fast all the time. As a matter of fact, right now we are in the middle of the 40 day Nativity Fast. We are encouraged to fast according to each of our own physical/spiritual abilities.
There are writings by the Desert Fathers and the different Saints that some would give up food for days, others would live on just bread and water, others would give up different kinds of food. (For example, we are encouraged to give up meat, oil, dairy, and alcohol during the Nativity Fast.) St. John Maximovich of Shanghai & San Francisco would often just eat one small meal a day.
I would not encourage anyone to begin a Fast without consulting his/her Spiritual Father/Clergyman to help assess your spiritual state first.
After all, if you say "I am going to eat nothing but bread and water for ten days" and you have never fasted before, you may get so discouraged half way through, you'll go on a binge.
Sometimes it's not so important as to what you're fasting from, but that you are keeping the spirit of the fast. That is, you are removing the things from your life that are pulling you away from God, and you are focusing more on scripture and prayer.
God be with you during this time.
In XC,
Maureen