The spiritual benefits of fasting and the calorie restriction diet arise because conductivity of nerve and energy goes up. Cell membrane fluidity increases because the cells are no longer coated with junk increasing the availability of receptors for hormones and neurotransmitters. The cells are better "informed" so metabolism improves and they can detoxify themselves properly so there are less stored poisons. This means that metabolism in general can occur at optimum efficiency thus increasing the conductivity of spiritual Presence.
That is the less calories one eats and the higher the nutrition then the easier it is for the body to run through all its cycles with full efficiency. If we start up the digestive process several times a day, every day of our lives, then the body doesn't have time for cleansing /repair/regeneration. So organs congest, plaques are laid, enzyme systems get exhausted and metabolism is generally interfered with. If we load our system with food day after day, then our body is so preoccupied with digestion that it doesn't have the energy, enzymes and immunity for higher functions such as building the "spiritual body," and for higher thinking, psychic and visionary capacities. Such unceasing digestion therefore reduces the amount of light/love flow through the tissues. We become largely a "digestive" animal, with little contact with our psychic, subtle and spiritual capacities.
In considering the need for maximum nutrition with minimal digestion, it becomes apparent that recreational eating is counter productive and will set us back spiritually and energetically. In the philosophy of the calorie restriction system, we need to refine our diet so that we are only eating the most vital, nutritious food, specific to the real needs of our body. This system is focused foremost on efficiency, and thereby getting the digestive process "out of the way" so that higher life processes and experiences can be explored.
This diet is not undertaken in a machine-like punitive fashion, but simply through a hypersensitivity to reality. Hypersensitivity to reality is nothing other than Love! The more perfect the flow of light/love through our tissues, the more spiritual-intuition and intelligence we embody, and the more awareness we can apply to "including and transcending" our digestive function. We use food for self-repressionwithout even knowing it. When we stop doing this we quickly become reacquainted with all our repressed urges and unease: loneliness, horniness, sadness, confusion and other uncomfortable emotions. The calorie restriction diet should enable us to plum the depths of our incarnation in a geometrically accelerating fashion.
Fasting cleans all body tissues including synapses, liver and blood which allows greater conductivity of energy and nutrients. Then a energy source is taken which doesn't weigh the body down such as fresh squeezed vegetable juice or fruit juice...this provides the energy for popping in a fasted-clean body. The mild stress imposed by fasting fortifies the body to stave off degenerative diseases. The continual low-grade stress seems to make the cells stronger.
Hunger increases blood flow in the hypothalamus and other limbic areas. Mark Mattson of the National Institute on Aging says that he believes that the mild stress of fasting increases protein synthesis in the brain. And these additional proteins increase the growth of new nerve cells, as well as shielding the cells from oxidative damage. So fasting increases brain function, offers nerve protection. With a calorie restricted diet there is going to be less oxidation in the body in general. The calorie restriction diet does have spiritual effects in its highest aspect, but that is usually not why people go this route. We usually do calorie restriction for longevity first, then health benefits second. You won't get optimum health out of simply dropping calorie intake.