Fasting and prayer are interlinked. Fasting and prayer have been linked together in almost every religion and every tradition of the world. No god is pleased with your fasting, only we are freeing our body from toxic elements. When the body is purified of toxins, thoughts become positive. When the body contains lots of toxins, and the pancreas, liver, and intestines are all full, your thoughts are also negative and unclear. Hence fasting is done to have a pure effect on the body, not to please God.
We make a lot of work with our liver, stomach and pancreas. If there was a labour court for the organs, then all these organs would have complained against you in that court. We do not allow them to rest at all. We eat and drink all day till night, and get our digestive system to work excessively. They need some rest and for this you need to fast.
Think about your school classes. In first period you feel very alert? First few sessions, or just before lunch. If you have a heavy breakfast, the first session can also be boring. And right after lunch you feel the heaviest and the most dull!
Do not fast like this
There are some rules of fasting, but people do not follow these rules either. People think that fasting means they can eat certain things and cannot eat certain things. You can eat lots of nuts and fruits, but do not eat cooked food, i.e. rice and bread. This is not fasting. Some people eat boiled potatoes and sweets and say that they are fasting. They are fooling themselves. Sometimes, some people who want to fast all day, get up before sunrise and squeeze themselves with food. Then they remain empty stomach all day and as soon as sunset, they again fill themselves with food. This is not a good way of fasting at all.
Be fast scientifically
Fasting should be scientifically. Some fruits should be taken with juice and water so that enzymes are produced in the body. Digested food is digested by this. Fasting should not be eaten late at night because the digestive fire is not there to digest it. People fast unscientificly. Fasting should be rational. Jews, Christians, Muslims, Hindus - people of almost every tradition do such wrong fasting. All of them should know the scientific way of fasting. The Ayurvedic method of fasting is clearly mentioned in the scriptures. Fasting with a little fruit, juice, water and lemon is appropriate. If the capacity of the body is there, one or two days fasting can be done only on water. Nirjala Ekadashi fasting should be ended with lemonade. We need to educate people about this. In the evening, when eating after a full day's fast, one should always take salad, fruit and some light food; So that the digestive system is relaxed.
When should one fast?
It is not necessary that you fast only when there is a religious occasion. You can fast at any time as per your convenience to clean the internal dirt and improve digestion. Fasting also keeps our mind healthy. It also benefits in depression and many problems related to the brain. This is why fasting has been associated with religion in our scriptures. If you meditate on a full stomach, you will fall asleep. This is why fasting is emphasized. It is said that when you are fasting, you can speak your prayers effectively because then your body is pure and your brain has enough rest. When the body is pure, then your prayer becomes authentic and deep. Your attention is best when your stomach is empty.