Usually, people eat so many carbs on the carb-up day/s, that when they fast for the 10-12 hrs between let's say Sunday and Monday morning - the blood sugar levels fall so low that Ketones start showing in the urine. Which is a false positive, and, yes, you need to deplete ALL muscle and liver glycogen before you're truly in Ketosis.
Usually, people eat so many carbs on the carb-up day/s, that when they fast for the 10-12 hrs between let's say Sunday and Monday morning - the blood sugar levels fall so low that Ketones start showing in the urine. Which is a false positive, and, yes, you need to deplete ALL muscle and liver glycogen before you're truly in Ketosis.
Basically, if you are in a caloric deficit - most of the time once your run out of that glycogen fuel the body supplements w/ free fatty acids. That's why high-carb diets are not always the best for fat-loss, not only due to fat-burning limitations, but also due to insulin surges.