What Are Fasting Phases and What Do They Mean?

As you fast, your body moves through a series of biological states. Nutrify tracks these as fasting phases and shows you which phase you're in as your timer runs. This article explains each phase and when it occurs.

How Phases Work in Nutrify

The fasting phase is displayed:

• On the circular timer (as a colored label beneath the gauge)
• In the phase description text below the timer
• In push notifications if Phase Change notifications are enabled

The arc color of the gauge shifts as you move through phases.

The Fasting Phases

Fed State (0 hours)

Your body is actively digesting food and using glucose for energy. Insulin levels are elevated. This is the state you're in when you haven't started fasting yet.

Early Fast (0-4 hours)

Blood sugar and insulin levels begin to drop. Your body is finishing digestion and beginning to shift fuel sources. You're still primarily running on the food you last ate.

Fat Burning (4-12 hours)

Insulin has dropped low enough for your body to start accessing fat stores for energy. This is often the goal for people doing 16:8 or similar plans - you spend several hours in this zone after an overnight fast.

Ketosis (12-16 hours)

Your liver begins converting fat into ketones to fuel your brain and muscles. Many people report improved mental clarity in this phase. This is where a standard 16:8 fast takes you near the end.

Autophagy (16-24 hours)

Cells begin a process called autophagy - recycling and removing damaged components. This cellular cleanup is one of the most-discussed benefits of extended fasting. You reach this phase only if your fast runs longer than 16 hours.

Deep Autophagy (24-48 hours)

Autophagy is more pronounced. Old proteins and organelles are being broken down at a higher rate. This phase requires extended fasting beyond 24 hours.

Immune Renewal (48+ hours)

Prolonged fasting triggers stem cell regeneration in some studies. This is associated with potential immune system renewal effects. Only reached on 48-hour or longer fasts.

Phase Thresholds Summary

• Early Fast - starts at 0 hours
• Fat Burning - starts at 4 hours
• Ketosis - starts at 12 hours
• Autophagy - starts at 16 hours
• Deep Autophagy - starts at 24 hours
• Immune Renewal - starts at 48 hours

Getting Phase Notifications

To receive a push notification each time you enter a new phase:

1. Open the Fasting screen settings (gear icon, top right).
2. Make sure the master Notifications toggle is on.
3. Enable the Phase Changes sub-toggle.

See How to Set Your Eating Window and Fasting Notifications for full details.

💡 Phase timing is based on hours elapsed since your fast start time, not the clock time of day. If you start a fast at 9 PM, you'll reach Fat Burning around 1 AM and Ketosis around 9 AM the next morning.

Need More Help?

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1. Open Nutrify
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3. Tap Help & Feedback
4. Tap Report a Bug or Request a Feature

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