BBC health has some good articles on it, check these links,
Also another good source is here: Quoting,
"Fasting is, without any doubt, the most effective biological method of treatment... it is the 'operation without surgery'... it is a cure involving exudation, reattunement, redirection, loosening up and purified relaxation. While fasting, the patient improves her or his physical health and gains much. But he or she will have neglected the most important thing if the hunger for spiritual nourishment that manifests itself during fasting is not satisfied." said Otto Buchinger, Sr., M.D., Germany's great, self-described "fasting therapist," who founded the most famous of several renowned, European Buchinger Kliniks in 1952.
Prolonged, scientific fasting has proven itself, over several thousand years, as humanity's oldest, fastest and most effective weight-loss, detoxification, healing and longevity-enhancing modality known to mankind - both curative, as well as preventive.
Likewise, despite all 3 Fathers of Western Medicine having fasted and having prescribed fasting (Hippocrates, Galen and Paracelsus, who declared fasting "the greatest remedy, the physician within"), the fact remains that symptoms-oriented trained U.S. physicians are also equally in the dark.
More resources: Healthier living through fasting
Essense science of fasting (more of spiritual)
From religious ground, fasting is not only islamic practice. Its also a essential tradition of Hindu, Buddhist, Jewish and Christian belief. A beautiful quote on fasting by a Saint, "Let us love fasting exceedingly, for fasting cures diseases, casts out demons, drives away evil thoughts, renders the mind brighter, the heart pure, the body sanctified, and presents man to the throne of God."
-- St. Athanasios the Great