1. Immediate energy source: After consuming the last meal, the body breaks down the carbohydrates into glucose, which is then stored in the liver and muscles in the form of glycogen.
In the first few hours of fasting, the body starts utilizing the immediate energy sources available, primarily from glucose in the bloodstream.
2. Insulin decreases: In the absence of food intake, blood glucose levels drop, triggering a decrease in insulin secretion from the pancreas.
Insulin is a hormone that helps transport glucose from the bloodstream into cells.
3. Glycogenolysis: With the decline in insulin secretion, the release of glucagon from the pancreas increases.
Glucagon is a hormone that promotes the breakdown of glycogen, which is the stored form of glucose.
The body taps into its glycogen stores to provide an immediate source of glucose for energy.
Glycogen is stored primarily in the liver and muscles, and is broken down into glucose molecules through the process of glycogenolysis.
This process leads to the release of glucose into the bloodstream to maintain blood glucose levels.
4. Lipolysis: Lipolysis occurs primarily in the adipose tissue, which is the main site of fat storage in the body.
Lipolysis is a metabolic process in which stored triglycerides, a type of fat, are broken down into fatty acids and glycerol, which are then released into the bloodstream.
5. Gluconeogenesis: The liver initiates gluconeogenesis, a process in which glucose is produced from non-carbohydrate sources.
The sources that are utilized by the liver to produce glucose include amino acids, glycerol and lactate. This helps to sustain blood sugar levels.
6. Ketogenesis: After approximately 12-16 hours of fasting, the body depletes its glycogen stores.
At this point, the liver starts producing ketone bodies from fatty acids through a process called ketogenesis.
Ketone bodies such as beta-hydroxybutyrate, become a major source of energy for the brain and other tissues.
7. Autophagy: During fasting, cellular stress signals increase, triggering a process called autophagy.
Autophagy is a cellular recycling mechanism where damaged or unnecessary cellular components are broken down and recycled for energy or building new molecules.
This process helps cleanse and rejuvenate cells, promotes efficient cellular function, and supports overall cellular health.
8. HGH (Human Growth Hormone): Fasting triggers an increase in the secretion of HGH by the pituitary gland.
HGH is essential for promoting tissue repair, maintenance, and growth.
When food intake is limited, HGH helps preserve lean muscle mass, stimulates fat breakdown and the release of fatty acids, and enhances metabolism to maintain energy levels.
9. BDNF (Brain Derived Neurotrophic Factor): Fasting has been shown to increase the production of BDNF in the brain.
BDNF is a protein that supports the growth and survival of neurons, it enhances synaptic plasticity, and promotes the formation of new connections between brain cells.
Increased BDNF levels have been associated with improved cognitive function, memory and mood regulation.
