I think you're right - that would be a miracle. I don't think we have the tech right now to use the sugar in such a way.

That's not entirely true. There are fuel cells which work by oxidizing blood. I can imagine that they are not efficient enough at this point, but it's a start.

Wouldn't it be easier to use ATP instead of Sugar?

You would need somewhere to generate the ATP. ATP doesn't flow around in our blood, but is generated inside cells for their own use.

https://en.wikipedia.org/wiki/Electron_transport_chain

I assume it’s hard to emulate cellular respiration in things that aren’t cells.

My money is that we invent this to combat/manage people's weight. A machine that slowly burns off excess glucose in the blood stream? Suddenly those extra calories aren't a problem!

(There are probably a whole host of knock on effects that I'm not considering. I'm not a biologist.)

Very interesting idea. It’s been ages since I took chemistry but I’m not sure what to break down. Glucose is C6H12O6. If we imagined nanobots that could break this down in any way (disregarding latent energy) the most obvious compounds are 6 water + benzene (which causes anemia) or 6 hydrogen and carbon monoxide molecules (which causes hypoxia).

We could follow traditional glycolysis but without a recapture method, would cells create excess ATP? What would that affect? Would it change the production of insulin and it’s affects on storing tryglicerides? I barely have enough knowledge here to ask questions let alone have answers.

The most obvious option would be turning it into lactic acid right in the end of the kidneys. Any option you choose, people doing that would better drink a lot of water.

Anyway, I'm not sure breaking glucose is that useful. Won't it just make people hungry?

The dream is a food prophylactic. Eat ice cream and decide that this particular meal won’t add calories.

Yes, that would be great. But you'll have to deal with much more than glucose to get that.

You should invent that!