The practice of fasting in Ayurveda traditions is believed to confer both spiritual as well as physical benefits.

‘Upvaas’ (upa= near, vaas= stay) or fasting literally brings one closer to God. Each day in the week is sacred to a particular deity and devotees can honor their favored God by fasting on that day. Monday is dedicated to Shiva; Hindu women typically observe a Friday fast to honor Shakti, the Mother Goddess in her many forms as Durga, Kali or Parvati. Thursday is sacred to Vishnu and Tuesday to Hanuman. Astrologically speaking, Shani (Saturn), one of the nine navagrahas (planets) is a troublesome influence; a Saturday (Shanivar) fast is observed to sidestep misfortune and ill-health.

Typically, fasting involves no intake of food during the day and ends with a single meal in the evening. Fasting is also undertaken on certain holidays like Navratri, the nine-day festival dedicated to Shakti, and Shivaratri, dedicated to Shiva. A fast ends with prayers and an evening meal consisting of sattvic (pure) foods associated with spiritual well-being.

Many fasts originate from myths propagated by ancient seers to draw ordinary people towards spiritual enlightenment. The concept of Brahman or Absolute Reality, for instance, cannot be easily understood by lay devotees. The prospect of a tangible gain, however, will attract them towards observing a practice, howsoever difficult. People fast for the birth of a child or achieving prosperity or success in some enterprise. In the process of fasting, a person experiences moments that take him beyond material desires, towards realizing Brahman. Regular observance of fasting thus inculcates spiritual growth.

Yoga and Ayurveda stress on fasting for physical and spiritual well-being. When the digestive system is rested, it burns off existing toxins in the intestines.  The lightness of being that is experienced leads towards spiritual clarity. Sipping decoctions of digestive ingredients like black pepper, ginger, and jaggery further clean up the body.