If your body is running gluconeogenesis do you have the same amount of blood and brain glucose as if you eat carbs?
Gluconeogenesis is protein to glucose metabolism when you eat too much protein. Gluconeogenesis cannot occur with lipid-metabolism. So eat no less than 70/30 fat/protein.
The answer is no, and that's why your body transitions over to using ketones for fuel when glucose is not immediately available in the quantities required for daily brain and muscle function. If you're eating carbs, your body can easily use 120g - 160g of glucose per day. But when you remove carbs completely, your brain needs about 40 g of glucose per day to survive and that's where the gluconeogenesis process come into the picture.
Just so that I can understand the dynamics here, if a person were deep into a keto diet so that they are just burning ketones - what would that do to a lab test for glucose? I mean I follow that keto and low carb should improve the glucose level considerably- but I dont think/dont know that people on keto are going from 90 to 20 on fasting glucose -note that I said I dont know. So even if a person dramatically lowers their glucose level, where would the remaining glucose even come from if they are just burning ketones? Another way of asking the question is: Assuming that a person is following a keto diet religiously, does the body just flip the switch over to burning ketones completely or is it still creating a little glucose/glucogen on the side along with ketones?
The process of using ketones for fuel happens over a course of about 3 days of religious carb starvation. But then there's another process in play which is called keto-adaptation, which refers to the point when the body has fully acclimated to using mainly ketones and stored fat as primary energy sources. This process takes 6 to 8 weeks to occur. As I stated above, even in a fully keto-adaptive state your brain STILL NEEDS GLUCOSE to function, which is approximately 40g of glucose per day. Ok, so if carbs are no longer around, you might be wondering how exactly the body can create glucose out of seemingly no available raw materials. Well, as it turns out, the body does have another raw material to use, which you've probably heard of whenever you get blood work done: Triglycerides. Triglycerides are stored inside of fat cells. A triglyceride is simply three fatty acids attached to a glycerol structure. You can imagine what this would look like if you had a boat called "The Glycerol" and you were pulling three skiers, each with their own rope attached to the boat. When the body burns fat for fuel, it needs to get rid of the skiers attached to the boat. So using enzymes, the body literally cuts the rope of each skier (fatty acid) until all three are gone and only the boat, or glycerol is left. The body then sends the glycerol boat up the bloodstream to the liver where the liver itself can convert that glycerol into glucose so the brain can function. The fact that glycerol from fat can be used to produce glucose in the liver is one of the reasons to explain why carbohydrates are not considered essential in human nutrition. What the body needs is glucose, and where that glucose comes from doesn't make any difference. Hope that makes some sense.
And by the way, just in case anybody is wondering what happens if you burn up all your fat stores and the body has no more triglycerides to convert into glucose for the brain? That's when the body will literally start to eat away at muscle tissue and internal organs in order to create the glucose necessary to survive which is often referred to as "wasting away". Death occurs shortly thereafter due to organ failure.
Reading this thread gives me that much more confidence in a well-balanced, sensible diet and moderation. I'm not drawn to playing things too close to the wire.
Very good indeed. Man, there is a certain beauty in the process. Good design. Years ago I would have just said that you can't get there from here- ie. you cannot end out with glucose without access to carbs or sugar. Having been around the block a bit since then I just move into asking how it is done rather than whether it can be done even if not logical on the surface. I have been through the inquiry/puzzlement of how the hell a man can still produce some androgens without testicles and how he can produce large quantities estrogen without ovaries. And I have been through the inquiry/puzzlement of how the hell woman can produce androgens without the male gear. And so on. So I now accept as a starting point that the body has complex backup generators and alternative pathways. Awesome stuff.