I agree with your summary.

The body takes in food and by the time it gets to the small intestine much of it is in the form of long sugar molecules which are then split up into small glucose molecules which are circulated by the blood stream. The brain takes what energy it needs as a priority but other cells need to be "unlocked" by a key to accept the fuel.

That is where insulin comes in. It is the key. Cells are unlocked by the insulin and the glucose fuel is taken in and the mitochondrtia convert that fuel into another fuel used internally (ATP).

Glucose left over is stored temporarily in the liver where it can be retransmitted between meals. If there is still glucose left over it gets put into long-term storage as fat. If you get too much fat the body becomes insulin resistant so more and more insulin is required to get the fuel into the cells. It is almost like a self-destruct mechanism.

Why does the body have such a dangerous mechanism built in? I think it is connected to hibernation! When it comes to winter, bears stuff themselves with food. They become insulin resistant so need to eat even more food to get the same amount of fuel into their cells. They can put on ten pounds in a day!

They eventually go to sleep and ketosis trips in, it is really an emergency mechanism, and provides glucose while they sleep. They wake up in spring and continue as normal. If we could crack that part then maybe we could fix Type 2 diabetes. It certainly puts ketosis, as in "keto diet" and intermittent fasting into perspective.

Type 1 is where the body does not actually produce any insulin in the first place so insulin injections are required to keep alive.

(Sorry, I have been reading up on the subject recently!)