What Happens With Fasting Biologically

When we observe fasting, that state is referred to as Postabsorptive state which we could just understand that it is a state after the absorption of food. This state is experienced 6 to 12 hours after eating which is why you would start to feel hungry at this time and it is at this time that we are officially fasting.

It is not like our food gets digested within the 6 to 12 hour mark, it has to do with running out of backup or stored energy where fat is the major stored energy of the body. When we fast, the triglycerides are broken down into fatty acids and glycerin which is used to provide energy for the body. In all these, the liver has a role to play as it would convert fatty acids into ketone bodies and this is the main energy source for tissues in the body.

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You know, scientific words can be confusing but not to worry much because I am here and I always love to help you breakdown words. When we say Triglycerides in this context, it refers to fat on the body. They exists as individual but come together to make one. In their individual state, they are referred to as fatty acids.

My body, and your body need glucose to function properly because it is the only source of energy it understands but when glucose isn't available, it reaches out to other sources like fat. Fat denser than glucose and jam-packed. It also requires a lot of energy to convert and so the body would prefer to have it as a last resort and in extreme case of starvation. When the body wants to use fat, it reaches out for Ketone Bodies, and Ketone bodies isn't the same thing as glucose.

When we start to fast, the brain starts to use ketone bodies and not glucose and that leads to the headaches you usually feel when you are fasting. I use to experience this headache whenever I am fasting or days when I am hungry for a long time because I couldn't access food or I have a lot of things to do that I need to complete before talking about eating. At this moments, there use to be this sharp headaches that comes and go.

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When Ketone body reaches the brain, they function differently from glucose triggering the Area postrema and there is a chance that you might have read that the Area Postrema has be implicated a lot as a chemoreceptor trigger zone for vomiting. If you didn't know that before, you just got a free lecture today from me.

Remember that I mentioned as we were going through this post that triglyceride is a combination of fatty acid and glycerin but we haven't discussed the glycerin. Glycerin on the other hand is converted to glucose through gluconeogenesis. When we fast, our blood sugar drops and so does our insulin drop and more sodium is excreted by the kidney. Nephrologist and Fasting Expert Jason Fung, MD. says that the some of the side effects of fasting that you and I feel such as headache, dizziness, and lethargy as a result of low sodium level in the body.

We ca say this makes sense because we know that sodium is critical along with other electrolyte in the body for some functioning of tissues such as muscle contraction, beating of the heart, and responsible for a host of brain operations. In case you haven't heard that fasting puts the body in a catabolic state, let me be your teacher very quickly. It causes the breakdown of things through processes like Autophagy which has to do with cellular cleaning.

Reference

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8754590/
https://www.nejm.org/doi/10.1056/NEJMra1905136
https://www.ncbi.nlm.nih.gov/books/NBK537133/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4635036/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6004924/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9407646/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3833266/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6324303/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5042570/