The 3 Phases of Fasting: And How to Get Kicked Out of Each One | Masterjohn Q&A Files #299
Sep 26, 2022
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The podcast discusses the three phases of fasting and the transition from a fasted state to a fed state. It explores the depletion of liver glycogen and the shift to using ketones as fuel. The role of body signaling in transitioning between fasting states is also explained, along with the importance of preparatory signals when consuming food. The different stages of fasting and the changes that occur in the body during each phase are highlighted, including hepatic glycogen, gluconeogenesis, and ketones.
The three phases of fasting include the clearing of the small intestine, depletion of liver glycogen, and keto adaptation with the brain using ketones for energy.
Transitioning between fasting phases requires a preponderance of signaling, and small factors like consuming a bite of food will not shift the dominant state.
Deep dives
The Three Phases of Fasting
There are three distinct phases of fasting. The first phase starts four to six hours after a meal when the small intestine is cleared out and the insulin to glucagon ratio decreases. Phase two begins approximately 24 hours into fasting when liver glycogen is depleted, and gluconeogenesis starts replacing it as the primary fuel source. The third phase, known as keto adaptation, occurs around day five of fasting. During this stage, the muscles and other lean tissues become resistant to ketones, using free fatty acids instead. The brain also switches its metabolism, with 75% of its energy coming from ketones.
Transitioning between Fasting States
Transitioning from one fasting phase to another is not a sudden shift but a spectrum of changes influenced by signaling in the body. While a small signaling factor, like taking a tiny bite of an apple, won't kick you out of a fasting state, it can affect the preparatory signaling for the upcoming fed state. The preponderance of signaling determines the dominant state and it takes the majority of signaling to shift from one phase to another. Going from phase one fasting to fed or from one fasting phase to another is unlikely to happen due to minimal changes in signaling.
Analyzing Fasting Phases
The first phase of fasting occurs within four to six hours after eating when the small intestine is empty, and the insulin to glucagon ratio decreases. After approximately 24 hours, phase two begins as liver glycogen is depleted, and gluconeogenesis takes over as the primary source of glucose. By day five, phase three, known as keto adaptation, is reached. During this phase, the brain switches to utilizing ketones, while other lean tissues utilize fatty acids. Transitioning between phases requires a preponderance of signaling and small factors like consuming a bite of food will not shift the dominant state.
Short answer: 4-6 hours after a meal the small intestine is emptied and the insulin-to-glucagon ratio declines; 25 hours after, hepatic glycogen is emptied; 5 days later the brain is adapted to ketones and gluconeogenesis reaches its minimal level. Moving from one to the other cannot occur with a small piece of signaling like the bite of an apple. It requires the preponderance of signaling. This is a clip from a live Q&A session open to CMJ Masterpass members. In addition to this episode, you can access five other free samples using this link:
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The 3 Phases of Fasting: And How to Get Kicked Out of Each One
If you want to become a Masterpass member so you can participate in the next live Q&A, or so you can have access to the complete recording and transcript of each Q&A session, you can save 10% off the subscription price for as long as you remain a member by using this link to sign up: https://chrismasterjohnphd.substack.com/qanda Learn more about the Masterpass here: https://chrismasterjohnphd.substack.com/about This snippet is from the July 13, 2022 AMA. The full recording and transcript is reserved for Masterpass members. Here is a preview of what’s included:
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