Your description of ketosis is pretty lacking. You never completely stop using glucose as a fuel source. In fact, your brain always has a requirement to get abo

Your description of ketosis is pretty lacking. You never completely stop using glucose as a fuel source. In fact, your brain always has a requirement to get about 30% of its energy from glucose and it takes up to 40 days to get to that point. You might be wondering how its possible to use glucose as fuel when you aren't eating any glucose, if so, look up Gluconeogenesis.