Chris Masterjohn Ph.D. is one of my go-to people for biochemistry lessons. He's a true geek, if I can put it that way.
Masterjohn did an entire series on energy metabolism, with emphasis on ketosis and ketogenesis. At one point in the series he discusses gluconeogenesis. In his opinion, gluconeogenesis is very expensive.
His explanation starts from the point that three steps in glycolysis cannot be reversed and:
"Getting around them requires four gluconeogenesis-specific enzymes and the investment of a much larger amount of energy. Overall, six ATP worth of energy are invested to yield glucose, a molecule that only yields 2 ATP when broken down in glycolysis." [source]
In this lesson he goes into details about these reactions and also why they involved a high energy (metabolic energy) investment). It follows that since the body spends such a big amount of energy to make glucose it goes to show how important it is for life.
Well, yes! It is essential, but this doesn't tell us how much or how little we should get from the diet and how good is the body at gluconeogenesis (making its own glucose) when no dietary carbohydrate is ingested.
I'd recommend watching the lesson if you're interested in the subject. One thing that I need to point out is that Masterjohn's graphics and slides are stellar and his method of delivery is very clear and straight to the point!
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Cristi Vlad Self-Experimenter and Author