As You Fast: The Physiological And Spiritual Principles Of Fasting

By Amy Malphrus MD and Rev. William E. Malphrus

Fasting is the practice of the voluntary cessation of nutrient intake for a set period of time. The Bible has multiple references to fasting, and the medical literature has numerous examples of the benefits of fasting. This book reviews the physical benefits of fasting. The manner in which fasting impacts some organ systems and disease processes are reviewed as well as what happens during the physiological process of fasting.This book also reviews the scriptural references to fasting in both the Old and New Testaments. The biblical indications for fasting are explained.The reader will see how the two overlap. The goal is to promote an understanding of spiritual fasting while also understanding the physiologic mechanisms associated with fasting and how the two possibly relate to each other. Once completed, the reader will have a better understanding of both the physical and spiritual principles of fasting.

• Language: English
• Publisher: Christian Faith Publishing, Inc.
• Release date: Mar 29, 2021
• ISBN: 9781098065539

Book preview

Chapter 1

Physiology of Fasting

Humans as well as other species have two forms of energy available to them. When we eat three meals a day, we are continually feeding ourselves glucose as a form of energy. This substrate is short acting.

Upon ingestion of glucose, insulin is released from the pancreas. The presence of insulin indicates a fed state. Insulin promotes the uptake of glucose for use by the body.

When there is excess glucose, it is stored as glycogen in the liver. Glycogen is released in times of food scarcity.

Several hours after a meal, blood glucose levels drop, signaling the release of the hormone glucagon. Glucagon is released from the pancreas. The presence of glucagon signals a starved state and signals the liver to convert the stored glycogen (the stored excess) into glucose. Glycogen stores are typically depleted after twelve to twenty-four hours.

Once glycogen stores are depleted, there is no more substrate to turn into glucose, and there is a metabolic switch. The liver begins the oxidation of fatty acids (non-carbohydrate sources). This is the liver using fat stores. Adipose tissue lipolysis (or breakdown) increases to produce more fatty acids and glycerol. These free fatty acids are transported to the liver where they are oxidized and made into ketone bodies.

Fat-derived ketone bodies as well as other substrates are used as a source of energy rather than using glucose when there is a switch from glucose metabolism to ketone metabolism.

The ketone production takes place in the liver. This is the adaptation used when food sources are not readily available. These mechanisms allow us to be able to continue to survive in the event of food shortages when glucose sources are not readily available.

Using ketones as an energy source changes multiple pathways. Scientists are still discovering all of the different metabolic and hormonal changes that occur when changing from glucose metabolism to ketone metabolism. One such example is a change in the genetic expression of certain factors, and the genetic expression of certain cell types also changes. While the benefits of fasting are too numerous to count and while books have been written about the biological changes that occur during fasting, we will only briefly highlight a few disease processes and how the physiology of fasting improves them (Rothschild n.d.).

Ketones function as more than just an alternate energy source for the body and, specifically, for neurons. The most prevalent of the ketones, Beta-hydroxybutyrate (BHB), also serves important neuronal signaling functions. In some neurons, specifically cortical and hippocampal neurons, BHB induces the transcription of brain-derived neurotrophic factor (BDNF). BDNF has many functions, including regulating neuronal functioning by stimulating mitochondria development, aiding synaptic signaling for learning and memory, and promoting the production and survival of new hippocampal neurons. It also is neuroprotective to injury and disease during a time of stress. If there are circulating ketones and the brain is injured, the resulting damage is much less with ketones present.

The mitochondria are the parts of the cell that are responsible for energy production within a cell. Systems that are high energy, such as the nervous system, have larger numbers of mitochondria. Fasting induces the expression of a regulator of the mitochondria, the PGC1 family, specifically PGC1α (PGC1α). PGC1α induces mitochondria formation, making more mitochondria, as well as detoxifying the cell, which in turn enhances neuronal energy and enables synaptic plasticity (Austin n.d.) (Phillips n.d.).

Neuroprotection is a way in which an environment is created that then protects the cell in the event of an injury. That injury can be of any type, such as trauma, lack of blood flow, accumulation of products, or anything else that might damage the brain cell (Tieu n.d.) (Bruce-Keller n.d.).

Through a number of neuroprotective mechanisms, intermittent fasting has been shown to reduce the volume of stroke during an ischemic event (arterial occlusion) and enhance the recovery. It has been suggested that ketones may improve outcome in traumatic brain injury and other nervous system injuries (White n.d.) (Manzanero n.d.) (Davis n.d.) (Plunet n.d.) (Prins n.d.).

There is evidence that intermittent fasting improves cognition as well as other neuronal signaling pathways due to activation of multiple pathways and through multiple mechanisms of action (Fontan n.d.) (Murray n.d.) (Kim n.d.) (Li n.d.) (Talani n.d.) (Halagappa n.d.) (Mattson n.d.).

One such pathway involves the aforementioned brain derived neurotrophic factor (BDNF). The BDNF is increased during times of fasting. Brain derived neurotrophic factor (BDNF) is a protein involved in learning, memory, and the generation of new nerve cells in the hippocampus. There is an increase in the thickness of the cortex in regions of the hippocampus during times of fasting. (Phillips n.d.)

An increase in BDNF has been shown to have an antidepressive effect. Indeed, fasting has been shown to have a mild euphoric effect. It is not clear if this is solely due to an increase in BDNF, as other neurotransmitters and signaling pathways also change when one fasts (Marosi n.d.) (Lee n.d.).

Animals have also been shown to improve their cognitive and motor capabilities through mitochondrial complex pathways and to reduce molecular damage. Animals have been shown to be more alert during time of fasting, allowing the animal to be more aware of predators and better able to hunt for prey (Singh