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by mercurialshark
1987 days ago
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I appreciate your comprehensive answer, it's very helpful. Question: > "you'll starve, or poison, the brain long before you manage to starve out a cancer. (Yes, Ketone bodies are a thing, but that happens alongside your body mobilizing everything it can to feed the brain, not instead of.)" Layman here, but my understanding is that depriving the body of the ability to replenish glycogen stores that are normally used for energy forces the body to metabolize fat in order to produce ketones, which in a ketogenic state, the brain is entirely fine utilizing as a primary energy source. Thus, if in a ketogenic state (or on a strict ketogenic diet), the body isn't being starved, just consuming stored energy reserves. Am I oversimplifying the concept? |
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You've got it essentially correct, it's just that every metabolic pathway is in a dynamic equilibrium. So let's say you do deprive the body of fresh glucose intake. While liver is turning fat into ketone bodies, and brain and skeletal muscle are digesting those ketone bodies, at the same time that TCA cycle that is now getting fed ketone bodies is going to push back upstream to tilt 'eat sugar' (glycolysis) a little bit more towards 'make sugar' (gluconeogenesis); meanwhile, other ketone bodies (dihydroxyacetone) are going to plug right into the gluconeogenic pathway.
The body will be making glucose where it can, because, if I recall correctly, red blood cells can't make use of ketone bodies, full stop. Some level of production must be maintained.
Which, in the body's parlance, is 'starvation'. If red blood cells are going hungry, from the body's perspective, there's a serious problem. But that's part of the difference between true ketosis and a ketogenic diet - the latter continues glucose intake, with a preference towards stimulating ketogenesis. The former is "oh fuck where's the glucose why can't I use the glucose aaaaaah!"
I gotta go refresh this now - you're painfully reminding me of how long it's been since I reviewed biochem.