Two types of fasting — and why they do different things

Intermittent fasting means compressing your eating into a shorter daily window — typically 16 hours fasted, 8 hours eating. You do this every day. Your body gets a break from digestion, insulin stays lower for longer, and over time it becomes a sustainable structure for managing calories without counting every meal.

Extended fasting means not eating for 48 to 72 hours. This is a different tool entirely.

With intermittent fasting alone, your body may partially draw on fat for fuel during the fasting window — but most people never fully deplete their glycogen stores in 16 hours. The metabolic switch to fat burning, where the body runs primarily on fat rather than carbohydrates, takes longer than a single overnight fast. You might be getting some of the benefit, but not the reset.

An extended fast takes you all the way through. By hour 36 or so, glycogen is gone. The body switches over. By hour 60, you have been running on fat long enough for the shift to take hold — and you have also learned something about hunger that changes how restriction feels afterwards.

This is why the FastNow protocol starts with an extended fast rather than easing in with 16:8. The extended fast is the entry point: a clean reset that puts you in a different metabolic state before the calorie phase begins. After that, intermittent fasting becomes the daily structure — the eating window you maintain to keep the system working.

They are not competing approaches. They are sequential. The extended fast opens the door. Intermittent fasting keeps it open.

The app tracks both. When you start a fasting session, you choose whether it is an intermittent fast or an extended fast. The timers, the tracking, and the context are built around both types.