I have read the studies they reference. You can't look at fasting strictly in the short term and you have to look at total caloric load. Fasting isn't any better than regular caloric restriction when you look at the human randomized control trials. Those are what matters most, not mechanism studies looking at isolated immediate effects or animal studies. It's not as simple as fat storage and fat burning mode. The types of food you eat, the volume of food, and activity levels all affect insulin response to eating.