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> The only way to get consumed fat into your bloodstream is to first convert it into sugar --- which itself burns some energy.

Fat does not get converted into glucose in normal conditions in appreciable quantities. It's used as-is, most of the body can directly utilize fatty acids as a fuel source.

Also, body has a lot of mechanisms to deal with sugar. It is normally stored in the liver and then released slowly.

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But it will always prefer glucose stores over fat.

And the muscles. You can’t fight or flight if you have to ask the liver to deliver glycogen. That’s how anaerobic exercise works. You have the fuel but not enough oxygen to burn it so you burn it fuel rich and oxidizer poor.

Not quite. The body will just enter ketosis if glucose and glycogen levels are too low.

The grandparent means something a bit different. Muscles can use glucose without _oxygen_ to get short bursts of energy quickly by rearranging glucose molecules (indirectly) into lactic acid.

Ketones can't be used for this purpose.

Glycogen is stored in the muscles and in the liver, not just the liver. The liver holds around half of your reserves.

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