It’s a question of the fuel the body uses, it can either use Glucose, or your Fat stores.
For most, the body tries to use Glucose first, then once those glucose stores are depleted, then it must use fat, and convert it into Ketones.
Once you body is fat adapted, it will use the fat stores quicker and become more efficient in using those fat stores for fuel.
However, it is also crucial that you consume certain nutrients to enable that process. That’s why I focus more on nutrients than calories, especially Potassium and Magnesium.
You’re right to keep the nutrients and minerals up. As well, we must eat the right kind of carbs to feed the gut bugs. They prefer the resistant starch, the kind we don’t digest so it goes into the lower intestine for them. The tougher parts of veggies, stalks, peels. Root vegetables, cooked and then cooled (like potato salad). On grains, the indigestible parts. Since low carbers eat very little to no grains, we can be very judicious and just add powders to water or cold beverages like inulin or (dirt cheap) potato starch. A teaspoon to a tablespoon a day. They need it and in turn when you feed them, they give you good immunity, digestion, and moods.