In the story I mention the role of insulin in fat storage and glucose metabolism. Here is a little more information on that (though still very much simplified).

Glucose is a double-edged sword. It is vital, in that some cells in our bodies can burn only glucose, but it also can cause a lot of damage. Our bodies have a complex regulatory system to keep our glucose in a healthy range.

In a metabolically healthy individual, glucose is usually found in a range between 70 and 100.

If our glucose levels drop too low, we can grow light-headed, weak, and cranky. If they drop very low we can go into a coma, and if they drop lower still we can die. So if our glucose drops too low, our bodies release hormones that stimulate the liver to break down glycogen (the storage form of glucose) into glucose and release it into the bloodstream. If that is not enough, the liver will be stimulated to convert protein into glucose and release it into the bloodstream. It is normal for those processes to occur when we are fasting or if we do not eat starch or sugar.

If glucose is elevated it can cause a lot of damage to our system (described in another post). When our glucose is elevated our pancreas releases insulin, which tells the muscles and other tissues to burn glucose, the fat cells to store fat, and the liver to convert glucose to fat.