Fasting is a symbol. Fasting signifies abstinence from lust. Physical fasting is a symbol of that abstinence, and is a reminder; that is, just as a person abstains from physical appetites, he is to abstain from self-appetites and self-desires. But mere abstention from food has no effect on the spirit. It is only a symbol, a reminder. Otherwise it is of no importance. [Abdu'l-Baha: Baha'u'llah and the New Era]
“…this material fast is an outer token of the spiritual fast; it is a symbol of self restraint, the withholding of oneself from the appetites of the self, taking on the characteristics of the spirit, being carried away by the breathings of heaven and catching fire from the love of God.” [Kitab-i-Aqdas, sourced from the small prayer book ‘A Selection of Baha’i Prayers and Holy Writings’]