When you feel that way, it's because your blood sugar is low - your body i quite literally out of fuel. Once you adapt to not constantly providing an easy source of carbohydrates, it will activate other metabolic pathways. That's when you can go for an extended period without food.
If you want a softer landing, I recommend the 16+8 fasting for a week before diving into multi day fasting. You eat at the latest at 20 (8pm), and not until 12 (12am) the next day. It will take some adapting, but it's better than the headache inducing "withdrawals" you'll feel jumping headfirst into 36h fasting.
If you want a softer landing, I recommend the 16+8 fasting for a week before diving into multi day fasting. You eat at the latest at 20 (8pm), and not until 12 (12am) the next day. It will take some adapting, but it's better than the headache inducing "withdrawals" you'll feel jumping headfirst into 36h fasting.