They don't. After about two weeks, your body will learn to convert fat to glucose*wink*
Important! Once a week, like sunday, have a refeed your first 4 meals. Eat you protein first, then eat any low fat carbs you want. Waffles, pancakes, rice ect. It doesn't matter.Don't stuff yiourself. Eat til you are full. Just NO fats with those meals. After meal 4 go back on the pro fat diet. No cardio on this day. No training. It defeats the purpose of the refeed.