Exercise effect on Ketone levels

How the body's energy systems interact with different types of exercise and states of adaptation, particularly in the context of ketosis and glycogen usage. 

1. Cortisol and Glycogen Release During Stress:

   • When the body is under stress (e.g., during intense exercise or a fight-or-flight situation), cortisol levels rise, and glycogen is rapidly converted into glucose to provide quick energy for muscles. This mechanism is essential for survival, allowing quick bursts of energy when needed.
     
     

2. Anaerobic Exercise and Glucose:

   • Anaerobic exercise, such as sprinting or lifting weights, relies heavily on glucose as a primary fuel because it requires quick, explosive energy. This leads to a decrease in glycogen stores.
     
     

3. Ketosis and Recovery:

   • After anaerobic exercise, the body prioritizes replenishing glycogen stores. During this recovery phase, ketosis can be enhanced as the body shifts to fat metabolism to support energy needs while glycogen stores are being restored.
     
     

4. Fasting and Ketosis:

   • Initially, fasting triggers the release of glucagon, which signals the body to release stored energy. Early in fasting, there may not be a significant increase in ketone levels because the body is still using glycogen and other readily available energy sources. As fasting continues and glycogen stores deplete, ketosis becomes more pronounced.
     
     

5. Cellular Adaptation:

   • The degree of adaptation of muscle cells influences how the body uses fuel:
     • Less Adapted Cells: These cells rely more on glucose, leading to quicker depletion of glycogen stores during exercise, which can increase ketosis as the body compensates by breaking down fat.
     • More Adapted Cells: These cells are more efficient at using fat directly for energy, even during anaerobic exercise. This reduces the reliance on ketone production during activity, reserving ketones primarily for brain function.
       
       

6. Rest and Ketone Production:

   • When the body is at rest after exercise, the priority is to replenish glycogen stores. If glycogen is low, the liver ramps up ketone production to ensure that the brain and other organs have sufficient energy, especially if the individual is fasting or on a ketogenic diet.

In essence, the body's response to exercise, fasting, and stress is complex and highly dependent on the metabolic state and level of cellular adaptation. Ketosis is a dynamic process influenced by the interplay between glycogen availability, fat metabolism, and the specific energy demands of the body at any given time.

When the cells are "more adapted", they could more readily use fat directly as fuel. This means that when doing aerobic exercise, fat will be used but directly from intra-muscular fat and not so much via ketogenesis in the liver. In this state energy is less dependent on the limit of glycogen storage in muscles and liver. 

So when the cells are "not so adapted" both aerobic and anaerobic exercise will most likely decrease glycogen storage and cause higher ketone levels when the body recovers.

When the cells are "more adapted", the muscles will use more fat directly and not "via ketones from the liver". Then the ketone production will mainly support the brain energy.

When the body then is at rest, refill of glycogen storage is prioritized and the ketone production to "cover" energy needs in the brain and other organs are increased.