STAGE 1: The Fed State (0-4 hours)
1. Increase in Blood Glucose: After consuming a meal, the body digests and absorbs the food, leading to an increase in blood glucose levels. This triggers the release of insulin from the pancreas to help facilitate the uptake of glucose into cells for energy or storage.
2. Glycogen Storage: Excess glucose is converted into glycogen and stored in the liver and muscles. Glycogen serves as a readily available energy source that can be quickly broken down into glucose when needed.
3. Fat Storage: Excess glucose that is not immediately used for energy is converted into triglycerides and stored in fat cells for future use.
4. Protein Synthesis: The fed state is a period of anabolism, where the body synthesizes and repairs tissues and proteins. Insulin promotes protein synthesis by facilitating the transport of amino acids into cells, supporting muscle growth and tissue repair.
5. Increase Energy Availability: As glucose is the primary fuel source during this state, the body relies on carbohydrates for energy. This leads to an increase in energy availability.
6. Lipogenesis: Lipogenesis, the process of converting excess glucose into fatty acids, occurs during the fed state. This contributes to the storage of fat in adipose tissue.
7. Absorption of Nutrients: During the fed state, nutrients such as carbohydrates, proteins, fats, vitamins, and minerals are absorbed from the digestive tract into the bloodstream to utilized by the body
STAGE 2: The Early Fasting state (4-24 hours)
1. Decreased Insulin: After your body has used up the glucose from the last meal, insulin levels start to drop. Insulin is a hormone that helps transport glucose from the bloodstream into cells.
2. Blood Glucose Decline: As the body exhausts glucose derived from last meal, blood glucose levels start to decline. This triggers the release of glucagon from the pancreas, which promotes the breakdown of stored glycogen into glucose in a process called glycogenolysis.
3. Glycogen Depletion: The stored glycogen in the liver and muscles the immediate source of glucose during the early fasting state. As glycogen is broken down, it is released into the bloodstream to maintain blood glucose levels and provide energy to the body.
4. Gluconeogenesis: After glycogen stores are depleted, the body starts producing glucose through gluconeogenesis. This process primarily occurs in the liver, where non-carbohydrate precursors, such as amino acids from protein breakdown and glycerol from triglycerides, are converted into glucose.
5. Ketogenesis: As the body transitions to using stored energy, it begins breaking down fatty acids from adipose tissue into molecules called ketone bodies. Ketone bodies, such as acetoacetate and beta-hydroxybutyrate can serve as an alternative fuel source for the brain and other tissues. This process is known as ketogenesis.
6. Lipolysis: During the early fasting state, lipolysis is stimulated releasing stored triglycerides from adipose tissue. Enzymes called lipases break down triglycerides into fatty acids and glycerol, which can be used for energy production or converted into ketone bodies.
7. Decreased Insulin Levels: In response to declining blood glucose levels, insulin secretion decreases during fasting. Lower insulin levels promote the breakdown of stored energy sources, such as glycogen and adipose tissue, to provide fuel for the body.
8. Increased Fatty Acid Oxidation: With the shift from glucose to fatty acids as the primary energy source, the body increases fatty acid oxidation, where fatty acids are broken down to release energy to meet the body's needs.
9. Increased Brain Derived Neurotrophic Factor: The production of Brain Derived Neurotrophic Factor (BDNF) a protein that promotes the growth and survival of neurons in the brain and peripheral nervous system may increase at this point. BDNF plays a crucial role in promoting neuroplasticity, synaptic plasticity, and the formation of new neurons. It is primarily produced and released in the brain, but it can also be found in other tissues throughout the body.
STAGE 3: The Fasting State (24-48 hours)
1. Continued Glucose Decline: As the body depletes its glycogen stores, blood glucose levels continue to decline. To prevent hypoglycemia, the body relies on gluconeogenesis to produce glucose from non-carbohydrate sources, primarily amino acids from muscle protein breakdown and glycerol from triglycerides.
2. Ketosis: With extended fasting, the production and utilization of ketone bodies become more prominent. Ketones provide an alternative fuel source for the brain, reducing the reliance on glucose and preserving glucose for tissues that require it. The brain, muscles, and other tissues start utilizing ketones to meet their energy needs.
3. Increased Autophagy: During the fasting state, the body activates a cellular process called autophagy. Autophagy involves the recycling and degradation of damaged or unnecessary cellular components. It is a crucial mechanism for cellular renewal, waste disposal, and maintaining cellular process called autophagy. Autophagy involves the recycling and degradation of damaged or unnecessary cellular components. It is a crucial mechanism for cellular renewal, waste disposal, and maintaining cellular homeostasis.
4. Hormonal Changes: Fasting triggers significant hormonal changes in the body to support energy balance and conserve resources. Insulin levels remain low, promoting the utilization of stored energy sources like glycogen and adipose tissue. Growth hormone levels increase, stimulating fat breakdown and preserving muscle mass. Cortisol levels also rise to mobilize stored energy and assist in gluconeogenesis.
5. Muscle Protein Conservation: While the body relies on gluconeogenesis to provide glucose during fasting, it attempts to conserve muscle protein as much as possible. The increase in growth hormone helps preserve muscle mass and shifts the body's energy utilization towards adipose tissue.
6. Reduced Metabolic Rate: Extended fasting can lead to a decrease in metabolic rate, as the body attempts to conserve energy. This reduction in metabolic rate helps to conserve energy stores and slow down the rate of weight loss during prolonged fasting.
7 Immune System Regulation: Fasting has been shown to have effects on immune function, including reducing inflammation and promoting immune system regeneration. The activation of autophagy during fasting helps remove damaged or dysfunctional immune cells, paving the way for the generation of new, healthy immune cells.
STAGE 4: Long Term Fasting (48-72 hours)
1. Ketosis Optimization: In the long term fasting state, the body becomes more efficient at producing and utilizing ketone bodies for energy. Ketones, such as beta-hydroxybutyrate (BHB), become the primary fuel source for the brain, muscles, and other tissues. This reduces the body's reliance on glucose and preserves glucose for tissues that require it.
2. Reduced Energy Expenditure: During long term fasting, the body conserves energy by reducing its metabolic rate. This lowering of energy expenditure helps to slow down weight loss and preserve energy stores. As the body adjust to lower energy intake, it becomes more efficient at utilizing energy and minimizing unnecessary energy expenditure.\
3. Muscle Protein Preservation: While the body continues to rely on gluconeogenesis to provide glucose for essential functions, it strives to conserve as much muscle protein as possible. The increase in growth hormone levels during prolonged fasting helps to preserve muscle mass. The body's primary goal is to utilize stored fat as an energy source and spare protein for vital functions.
4. Autophagy Maintenance: Autophagy, the cellular recycling and renewal process, remains highly active during long-term fasting. The breakdown of damaged or unnecessary cellular components continues, contributing to cellular rejuvenation and optimizing overall health. Autophagy is crucial for removing dysfunctional protein, clearing out toxins, and maintaining cellular homeostasis.
5. Immune System Regulation: Fasting has been found to positively influence immune function, even in the long-term fasting state. The activation of autophagy helps remove damaged immune cells and promotes the generation of new, healthy immune cells . Additionally, fasting may reduce inflammation and support immune system regeneration.
6. Hormonal Adaptations: Hormonal changes continue to occur during long-term fasting. Insulin levels remain low, promoting the breakdown of stored fats for energy . Growth hormone levels remain elevated, aiding in the preservation of muscle mass and supporting fat utilization. Cortisol levels may fluctuate and gradually decrease over time.
7. Increased Fat Utilization: As the fasting period extends, the body increasingly relies on stored fat as the primary source of fuel. Triglycerides stored in adipose tissue are broken down into fatty acids and glycerol, which are then utilized for energy production through a process called lipolysis.
8. Maintenance of Energy Balance: The body continually adapts to maintain energy balance during long-term fasting. While weight loss occurs, the body adjust its metabolic rate, energy expenditure, and fuel utilization to ensure a sufficient energy supply to vital organs and functions. This adaptive response helps to sustain the fasting state without compromising overall health.
9 Increased BDNF-Brain Derived Neurotrophic Factor: The production of BDNF will continue to further increase throughout your long-term fasting state.
