Let us share what we know about fasting in various religions whether mandatory or voluntary, how many days, specific time of the year and calendar followed (solar or lunar) etc.
Muslims follow the Islamic Calendar based on lunar year. They fast in the 9th month (Ramadan) which is mandatory. In addition Muslims can fast voluntarily for spiritual enhancement on any day except the two Eid Days falling on the 1st of Shawwal, the month following Ramadan, and the 10th of Zil-Hajj the last month of Islamic Calendar. Fasting on for six days in the month of Shawwal and 9th & 10th day or 10th & 11th day of the first month called Moharram, The day of Arafah (9th of Zil-Hajj) and some other days is considered to be of great benefit and is considered to be a source of pleasing the God.
Fasting is disliked on the last days (29th & 30th) of Ramadan or on Fridays as a habit. It is also prohibited to single out Saturdays for voluntary fasting. Perpetual fasting is also forbidden.
The time of fasting is from the Morning when it is still absolutely dark till the sunset and during this period a Muslim cannot eat, drink or have sex.
In Western forms of Protestant and Catholic practice of Christianity, fasting is an optional-only practice that is infrequently used and for which there are no longer any governing rules. This said, there are Western Christian monastic orders that still practice ritual fasting, though this underscores the fact that ritual, organized fasting has all but vanished (if not completely vanished) from Western Christianity. Yet there are Western Christian individuals who choose to practice one form or other of ritualized (as opposed to sporadic or dietary-use) fasting.
I believe, as post 2 has suggested, that fasting is less central to modern Christianity, especially Protestant Christianity, than in some other faiths. (Of course, there is Lent, but I don't think that qualifies, at least in the terms suggested by the original post.) I do know that fasting was often discouraged by early Protestants, especially Puritans, who viewed it as essentially ceremonial in nature, associated with the holy days they saw as overly secular.
There is some fasting in Christianity, but it does not seem to be as organized. It seems like fasting is a way to purify and humble oneself in each religion.
I'm a Christian and I've never come across another Christian who is fasting because of their religious reasons. Some might, but I think it's very rare, and depends on which groups of Christians you are around, because being called a Christian is a very general statement.