Firstly, you don’t need vegetables at all. People have lived on plant-free diets for decades and been fine. There is no known disease of carbohydrate deficiency, and if there were, I’m pretty sure it would have been discovered by now.
The point of a ketogenic diet is to avoid sugar, grains, and starches, because they are very rich in glucose, which drives up blood sugar. Elevated blood sugar results in elevated insulin, and the two of them together cause damage over time, as well as promoting fat storage. So we recommend that, if you feel you need to eat vegetables, they should be ones that grow above ground, because they tend to be lower in digestible carbohydrate.
As for fat, you need only enough to satisfy your hunger. Fat has a minimal effect on insulin, so it thus becomes the safer energy source to replace the calories lost from lowering carbohydrate intake. Fat is not magic, so you don’t want to eat more than your appetite requires.
Try the following: eat very little carbohydrate, a reasonable amount of protein, and enough fat to satisfy you. (There is, as you will discover, a big difference between eating till stuffed, and eating enough.) If you find yourself needing a snack, either make it something carb-free, or make a whole meal for yourself. (There is no need to eat according to the clock.) If the food stimulates your appetite, then eat the meal until you stop being hungry again.
There is no need at this point to limit yourself to an eating window, or fast, or any such thing. Eat when hungry, stop when no longer hungry, wait until you are hungry again before eating again. I think you will find that, while you may find yourself eating more than you think you should be, your body knows what it wants. Once it is assured of a reliable food supply, and that the famine is over, your appetite will most likely spontaneously drop. It works that way for most people, at any rate, though a few people find they cannot trust their appetite hormones.
