Navratras come twice a year and mark the transition of the seasons. Ayurveda recommends the consumption of nourishing foods in minimal quantities to detox the body during this time. The nine nights and 10 days hold the energy of 10 forms of Shakti—Shailaputri, Brahmcharini, Chandraghanta, Kushmanda, Skandmata, Katyayani, Kaalratri, Mahagauri, Siddhidatri and Aparajitha. During the Navratras, the weather changes—various energies move from imbalance towards a new normalcy, including in our body. The prana shakti undergoes a process of re-alignment. The body has to be kept light. This is why our ancients prescribed fasting for nine days. Upavaas has a much greater connotation than merely abjuring certain foods. At Dhyan Ashram, sadhaks observe upavaas in its aunthentic sense—giving up pleasure to observe austerities during sadhna, by being celibate, eating for energy and not sensual pleasure, following a niyam of the sadhna your Guru has given you—a mantra, dhyan or tantric practice where the senses are kept under strict control and the focus is on your ishta deva. Charity and service are a must. These fasts are for purification, both etheric and physical.
Apart from fasting, there are detox mantras too. For the beginner, these nine days may be divided into three parts of three days each for the three parts of the body—the region below the navel, between the navel and the shoulders and the upper head region, corresponding to the energies of the goddesses Sarawati, Lakshmi and Durga respectively, who arise from the Adi Shakti. These three parts are further divided into three more, thus dividing the body into nine parts.
In the first three days, the sadhak stops consuming spicy food and performs a havan in the morning and dusk with chants invoking Ma Durga. The offering of kala til along with ghrit is made and the upla and palash samedha from Indian cows is used.
In the next three days, the sadhak avoids grains and only light foods are ingested. A havan for Ma Lakshmi is done at twilight by making offering sweets along with ghrit. In the last three days, the sadhak only consumes water and fruit juices and havan for Ma Saraswati is performed at twilight, making offerings of ghrit and guggal. The tenth day is the day of complete fasting and once more both goddesses Ma Durga or Ma Kali are invoked as it is on this day Ravan had invoked them. This process brings about the required re-alignment. After this, the sadhak chants the specific mantra as prescribed by his/her Guru.
With yog sadhna, all the energies invoked come to the sadhak. Navratras are days to prepare your body in order to accept the new energies of the coming season. For nine days you re-align your body and after that on the tenth day accept new energies.
Most people fast for nine days to lighten their bodies, only to make it heavy on the tenth by going to restaurants and bars. It is like cleaning your room and afterwards bringing all the garbage back. Fasting or any such technique will bear fruits only if carried out with detachment, for the purpose of evolution. The Guru knows the capacity of a shishya and prescribes the kind of fast depending upon his/her requirements. It is of utmost importance to observe fasts in tandem with yogic practices such as the Sanatan Kriya under the sanidhya of a Guru to reap maximum benefits.