There are several consequences of a 40 day’s fast, in case of an average person (no chakras fully activated, no yoga practice).
The brain needs around 100 g of glucose daily, for it’s various purpuses. It’s only fuel is this substance. If it does not come with food, the body will try to get it from what it can.
The glucose (glycogen) deposits in muscles and liver are the first used in case of fasting. Than an interesting thing happens … the usage of fat deposits is slow. Because of this, in case of fasting, rather than to reduce brain activity, the body will start to use up muscle mass, at around 100 grams/day (as syntesis from proteins is faster than that from fat, and 1 gram of protein is aproximatley the same calory count of 4 than glucose.) So in the beginning phase, musclemass is used, for a few days, than, when the body realizes that the fasting will continue, will try to prevent loss of muscle mass by reducing both brain and muscular activity. A certain lethargy sets in. So by fasting, the mind and body (the senses) are dulled and put to rest, this way a ceirtain autonomy of the soul/consciusness is gained. From this moment, the body’s resources are used up in a much slower rate, but their amount expire around the 40th day, and the body perishes.
It is important to note that the really first proteins to be used up are the digestive enzymes, so getting back to normal feeding must be gradual, to prevent death by autointoxycation.