"In all religions, they recommend fasting. But there are some rules for fasting. It is not that you should not eat all day and then eat a lot at night. Sometimes in Navratri in the name of fasting we feast.We eat potatoes, fried food, french fries.This is not correct.This is a wrong type of fasting. You should not fast like that.A little bit of food and food which is easily digestible. A little bit of fruits and drink a lot of water. When body is not so heavy or dull, then it blossoms and meditation happen better.Isn't that so. How many of you have this experience. At the same time too much fasting will raise the pitta in your body." -- Sri Sri Ravi Shankar
Fasting is an ancient method to detox prescribed by Ayurveda per body type, dosha (Vata, Pita, Kapha). Having no food increases acidity, it's very bad (Tamasic)!
One should have more alkaline fruits and vegetables, cucumber, watermelon is very good.
In general khicchadhi is used in Ayurvedic detox diet and used in Panchkarma.
One needs to first know ones doshas. For example, if you have Kapha dosha, to restrain from deep fried food, have green beans, carrots, and so on.
It's also necessary to have lots of fluid, 6 - 8 glasses, to wash away the eliminated toxins and reduce the taxing on the liver and kidney. Certain juices maybe good for certain body type and ailments. Coconut water is very good, and a complete meal.
Fasting means to eat healthy, low carb diet, fresh fruits and vegetables, nuts, protein, healthy food, which is essentially called a "Sattvic" diet in Ayurveda.
It's not a to starve yourself to please a God. Ancient teachers linked it to God, like Tuesday for Hanuman, etc. so that people would fast. Starving yourself is not good. Now fasting has become ritualistic and dogmatic without people understanding the true meaning behind it.
A lot of people will eat unhealthy food as mentioned by Sri Sri. Nowadays you see a lot of detox diets. That's exactly what the ancient method of fasting was. If we can't practice the ancient methods correctly and they have become corrupted let's follow the new modern scientific method which is essentially "Punarnava" the old method renewed.
It was said that we should fast on the elevanth day of the lunar month, "Ekadashi." Why? Because certain cronic ailments peek either on no moon night or full moon night.If we eat a detox diet three days prior to the no moon or full moon night, our ailments will be reduced because it takes three days for that to reach all the cells of the body. It is very scientific.
The human body is a good conductor of life force energy, prana. When the cells are not burdened by digesting food, the cells then turn to conducting more energy and can survive on it. It raises the energy Prana in us. This is why having a light stomach is good for meditation as well.
Navratri is a good time to do a complete detox of the enter system. Fasting is a good time to do complete cleansing on all levels - it's not just refraining from food, but to be in a pure state of being. It is to raise the Sattva (purity), remove impurities (Tamas) and imbibe good qualities (Rajas). There's no point in not eating, yet being angry, or worried, or doing non-sattvik things.
Purifying on body level through yoga, fasting (detox). It is good to fast for at least 3 days because it takes that much time to be cleansed down to the cellular level. It's the same in Ayurveda's Panchakarma.
On the breath level through Pranayama; on the mind level by turning the senses inwards, showing restraint on our speech, and keeping the senses in check. Purifying emotions through devotion, Puja, Kirtan/Satsang. Keeping the intellect engaged in spiritual knowledge. All the detox/purification makes it easy for us to be in awareness and meditation goes much deeper.
This gives all our levels of existence deep rest and rejuvination. It's a good time to go to a spiritual retreat for a few days or to an Ayurvedic Panchakarma. Fasting and spiritual pracitices during Navratri, Ramadan, Pentacost, were meant for yearly detox. So if we do this during Navratri then we will be renewed by Dussera!