Producing ketones because your body is starved for sugars is different from full ketosis which your body goes into when fasting. It is only in full ketosis that the energy that normally goes into digestion can be redirected elsewhere, and some organs will even take on different roles during this time to aid in autolysis or detoxification. This just doesn't happen when you trick the body into producing ketones otherwise. Fasting is a natural process, ingesting foods which have partial nutrition or no nutrition isn't and who knows what it will do to your body, nothing good I'm sure.