You need to start with the basics: https://en.wikipedia.org/wiki/Hypoglycemia https://en.wikipedia.org/wiki/Hypoglycemia and https://en.wikipedia.org/wiki/List_

You need to start with the basics: https://en.wikipedia.org/wiki/Hypoglycemia https://en.wikipedia.org/wiki/Hypoglycemia and https://en.wikipedia.org/wiki/List_of_causes_of_hypoglycemia https://en.wikipedia.org/wiki/List_of_causes_of_hypoglycemia Note how both articles don't talk about fasting or ketogenic diets. Basic idea: even a low blood sugar level (let alone 0) is very very bad news. The metabolism will do its utmost to make glucose, even from amino acids. That's why even people who eat nothing don't have hypoglycemia all the time...