Low Carb Math
wabmester
Posts: 2,748 Member
How low is too low? A little back of the envelope math may help.
The brain normally runs on about 120g/day glucose. Source
In ketosis, some sources say the optimal balance between ketones and glucose in the blood is 50/50, but let's go with Wikipedia, that says your brain can run on 70% ketones.
So, 30% glucose = 40g/day carb.
40g should be close to optimal for maintaining ketosis. If you consume less than 40g per day, your body has to make glucose from proteins (perhaps from fat too, but that's less efficient).
So, the normal calculation for "adequate" protein goes out the window if you eat less than 40g carb per day. You'll need more protein.
The brain normally runs on about 120g/day glucose. Source
In ketosis, some sources say the optimal balance between ketones and glucose in the blood is 50/50, but let's go with Wikipedia, that says your brain can run on 70% ketones.
So, 30% glucose = 40g/day carb.
40g should be close to optimal for maintaining ketosis. If you consume less than 40g per day, your body has to make glucose from proteins (perhaps from fat too, but that's less efficient).
So, the normal calculation for "adequate" protein goes out the window if you eat less than 40g carb per day. You'll need more protein.
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The brain may normally run on 120g glucose per day, but what portion of that do ketone cover when you're in ketosis?
Eta: brain dead, already answered. D'oh!0 -
So, the normal calculation for "adequate" protein goes out the window if you eat less than 40g carb per day. You'll need more protein.
Phinney & Volek mention that gluconeogenesis can use "metabolic leftovers". Also once you're keto-adapted, FFAs are used in many processes. Point is, moderate protein is ok. (I suppose it depends on one's definition of "moderate")
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Not sure what a metabolic leftover is, but I imagine they're referring to the glycerol used to hold together triglycerides.
The basic point here is that lower ain't necessarily better. The studies I've seen that show a higher level of cortisol on LCHF suggest to me that there's higher catabolic activity. Seems reasonable to minimize that if you can.0 -
I don't know about anyone else, but I read that as "low carb meth" for some reason. LOL!0
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No, this is not a recipe thread.
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sljohnson1207 wrote: »I don't know about anyone else, but I read that as "low carb meth" for some reason. LOL!
I literally cackled out loud at this. My dogs are now concerned about my sanity.
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Chalk it up to finally finishing Breaking Bad, all 6 seasons. I know, I'm behind the curve.0
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Ahead of me. I've never seen any of them!0
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How low is too low? A little back of the envelope math may help.
The brain normally runs on about 120g/day glucose. Source
In ketosis, some sources say the optimal balance between ketones and glucose in the blood is 50/50, but let's go with Wikipedia, that says your brain can run on 70% ketones.
So, 30% glucose = 40g/day carb.
40g should be close to optimal for maintaining ketosis. If you consume less than 40g per day, your body has to make glucose from proteins (perhaps from fat too, but that's less efficient).
So, the normal calculation for "adequate" protein goes out the window if you eat less than 40g carb per day. You'll need more protein.
So does this explain why I'm keeping FA within thumbrule of >100 g carb a day, as long as I burn off and reduce liver and muscle glycogen with intense cardio on a regular basis?
I also do IF, which should boost ketones production too.
Edit: Or is it that the reversal of mitochondria energy burning on ketones is NOT an overnight situation and I never stay out of NK long enough for that to happen ?
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What happens to people with large or small brains? Faster or slower thinking, movement, breathing? All of those things require brain function, (synaptic transmission).
That may account for quite a variation in glucose requirements. 0 -
There is significant variation in brain glucose requirements. Not just brain size, but age, gender, and even how long you sleep. But to justify going as low as 20g/d carbs (which a lot of people seem to do), you'd need a half-size brain.
@foamroller, during ketoadaptation, the mitochondia apparently change. There's both an increase in number, and an increase in enzymes to support FA oxidation. I assume the old pathways are still supported, but not sure how quickly we can adapt.
Cool article with some evidence from mice models:
http://caloriesproper.com/ketoadaptation/0
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