If meditation functions like a sort of psychic reset switch, and a method of accessing and transforming one's deeper mental functions, fasting seems to function as a physiological reset switch, and a method of experimenting with and exploring physiological reactions to food, and of course, the lack of food.
If you think about it, eating regularly results in an almost constant process of digestion, in which overlapping effects of various foods and liquids are always interacting with each other, and obscuring each other, so that it is difficult to get a handle on what foods are doing exactly what.
And our modern diets can be very complex. We have at our fingertips many different types of foods with many different types of ingredients, undergoing many types of processes, all of which put varying loads and metabolic requirements on our digestive system. And we may consume considerable clusters of these elements in a single sitting.
I spent a week with a partial fast, or subsisting on very little calories, to ease into a week of juice fasting - I'm not sure anymore that juice is a great idea for this - and it was very interesting to feel the effects of an occasional apple, salad, or egg. Various foods have their differing payloads of energy, and differing effects on the digestion system, which can be distinctly felt, depending on where the body's energy is diverted and committed to the various processing organs, and what exactly enters the bloodstream, which of course makes its transit throughout the body, and contributes to certain global effects.
There are of course problems with these self-experiments and observations. The body's stomach contains an ecosystem of its own, which is altered or even reset as the stomach completely empties in the course of a fast, so each subjective observation has to take place within the bounds of a system that is changing, and is either working on convention, slowing down, dormant, or speeding back up, among other possible dynamics, and the totality of these effects work on the mind itself, and enter into a feedback loop with the mind. It will always be difficult to determine exactly what is happening.
It is also possible that during the course of a fast, when energy is being diverted away from the stomach, the body begins using the energy to clean and process unresolved food stores, and expel toxins from the tissue, much like the brain expels toxins during sleep, a hypothesis that could be confirmed with oral and body odors, various discharges, and sudden spurts of energy, clarity, and vigor reported by fasters on the second week and on. Part of what kills people when they starve is the toxic shock when the body begins its cleansing process. With healthier bodies, and abundant water for the cleansing process, fasters can last as long as 40 days, which is the outer limit for safe fasting. After that it seems the starvation process truly begins, but some human beings have made it past this threshold.
One takeaway from this observation is that our constant exposure to numerous toxins and contradictory elements - which produces the physiological schizophrenia of the modern industrial subject - makes us much more vulnerable to a variety of maladies, despite a preponderance of resources. Though of course we could beg the question of what exactly constitutes a resource, considering that our manufactured goods fall apart out of the box and our industrial agriculture poisons us.
Moving on, when you disrupt your eating habits, it casts into relief just what exactly those habits are. What do you hunger for? What do you reach for? How do you eat? I've found that I constantly overeat, not out of sheer gluttony, but because my OCD compels me to finish everything, and I haven't yet learned to measure out proper portions. A corollary to this is that I eat too fast, so the signal that the stomach is full comes too late, and unsatisfactorily chewed food may make its way through the system only partially processed. There are other factors and tendencies at work as well.
Considering that fasting addresses the mastery of the will over one of our greatest drives, the hunger drive, it is also a good way to build on the faculty of the will in general, which of course has global benefits whenever the will happens to be exercised.
The will is often difficult to modify in isolation. The things that one is compelled to do, such as eat, drink, maintain shelter, and meet social obligations, exercise the will in their own way, so as to bring about the success of these things, but as soon as one attempts to develop some discipline or meet some requirement outside of these pressures, one finds one has to double one's efforts. These requirements grow proportionally to the complexity of one's living environment, and the more one is expelling one's surplus energy in various avenues.
This is because the regular exercise of the will to meet certain recurring bare requirements and obligations begins to carve out pathways for its regular exercise, which allows it to function with greater ease and spontaneity to achieve perpetual success. It generates convention.
To fast is to completely invert the logic that the drives perpetuate. One is beginning to fight against one's drives, and thus, the conventional structure of one's life, unless fasting is a ritualistic component of one's religious social obligation structure. This of course assumes a conceptual model in which the drives are actively shaped and directed by one's society and environment. Perhaps to better explain, the drives are very honest in their desire, but executive functions necessarily develop around one's drives so as to direct them, to repress or amplify them, so that one can move with relative harmony within one's natural and social environment, and these functions have to be taken with the drives in a complex society, perhaps to be understood as overriding drives of their own.
So to bring all of this together, to fast is to modify the executive functions by diverting energy from them, therefore making them more dormant and malleable. It is a way of tampering with one's physiological - and at times psychological - structures of convention and habituation, a desire, a drive which can only be generated through the failure of convention itself, granted that this practice is not already a part of one's habituation.
Further, it seems as though when you fast, energy is first diverted from energy-intensive higher brain functions - which are perhaps not immediately useful to survival - to lower brain brain functions, much like what happens during meditation, or after ingesting psychedelic drugs. The visual and perceptive systems feel especially vibrant and immediate, and visual awareness is sharpened. One's thoughts drift away from abstractions and anticipations to favor one's immediate reality. And supposedly in its advanced stages, intensive fasting can lead to profound spiritual experiences. It becomes more understandable as to why fasting has been so common to various religious traditions for thousands of years.
The practical and health benefits of fasting are still unknown; understandably the practice has not been rigorously researched, though it has been found that about 3 days of fasting can reboot the immune system. The same goes for the experimental opportunities behind fasting, and whether these opportunities can provide genuine physiological and psychological insights, or mere distortions. Still, there is a decent constituency that swears by its spiritual and physiological benefits, and it remains a time-tested tool, to use with other tools, to attempt to shape one's own life.
