Question: Why are medium-chain fatty acids ketogenic even in the presence of carbs?
It's all about the ratio. We know for a fact that MCT oil is ketogenic even in the presence of pasta, period, end of story. So, the question here is, biochemically, why is it happening? Well, they go into the mitochondria, even in the presence of insulin and a buildup of acetyl CoA over the incoming oxaloacetate. A high acetyl CoA-to-oxaloacetate ratio generates ketones.
So the question is that basically this question is why isn't there enough oxaloacetate? So generally insulin is going to favor the burning of carbs. And so generally when you have a large input of carbs, you have production of oxaloacetate, but the metabolic conditions are favoring you burning it for energy, not you producing oxaloacetate. And I think it's just a matter of the ratio and the speed at which things come in. And so if the MCTs are coming into the mitochondrion fast enough, and they're exceeding the rate at which oxaloacetate is produced, which is a likely scenario given that A, production of oxaloacetate from pyruvate is quantitatively minor anyway, and then B, in the presence of carbs stimulating insulin, you're going to get the pyruvate even more preferentially burned for energy.
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DISCLAIMER: I have a PhD in Nutritional Sciences and my expertise is in performing and evaluating nutritional research. I am not a medical doctor and nothing herein is medical advice.