What happens in the body during fasting?

During fasting, the body first uses the energy it has already taken from food. As insulin levels fall, fat burning begins, and blood sugar balance changes in the first few hours. In the later hours, glycogen stores in the liver decrease, and the body starts relying more on fat for energy. The text says snacks can interrupt this process by raising insulin levels. It also notes that the body's natural GLP-1 mechanism may activate, which can reduce the feeling of hunger.