I thought it was interesting to learn more about ketosis in class, especially because most of what I knew about it came from pop-culture and I had heard about the “keto diet” through endorsements, or seeing products labeled “keto-friendly” snacks. And because of that, I had mostly associated ketosis with diet culture rather than with any real biochemical or medical context. However it was interesting to learn more about ketosis from a biochemical basis and think about important therapeutic uses too. It is interesting how during fasting or low-carb diets, the citric acid cycle intermediates become depleted and the body shifts from glucose toward using fats for fuel, leading to ketogenesis. Some of the acetyl-CoA produced from fatty acid degradation is converted to ketone bodies, which then act as an alternative fuel source. I had heard about “entering ketosis” from a relative who fasted to reduce inflammation for arthritis, but I never understood what was happening in the body. Now it makes sense that there’s a genuine metabolic switch as the body transitions away from glucose.
I also learned that this adjustment isn’t immediate, and people often feel lethargic during the first couple of days because the body is changing its primary fuel source. What surprised me most was how efficient ketone bodies are as fuels, Since β-hydroxybutyrate and ketone bodies are water-soluble, they can be transported easily as respiratory fuels. Ketogenic diets take advantage of this by providing high fats and very few carbohydrates, pushing the body into a “starvation-like” state where fats and ketone bodies dominate energy production. It’s remarkable that after a few days of starvation, even the brain begins to rely heavily on ketone bodies. At the same time, learning about ketoacidosis helped me understand the limits of this system, and that too many ketone bodies can be harmful.