A FREE, CLINICALLY-INFORMED FASTING TOOL

Stop guessing
when to eat.
Start measuring
when to fast.

Everyone wants the fat-burning, autophagy-triggering state fasting produces. Almost no one knows exactly how long to fast, when to break it, or how to confirm they got there. We fix that in five questions — free, no catch.

100% FREE · takes 90 seconds · single printable page, no app required
Metabolic Clock
Illustrative model
00:00:00
Fed State
Fed (0–4h)
Glycogen depletion (4–12h)
Lipolysis rising (12–16h)
Ketosis (16–20h)
Autophagy (20h+)

WHAT'S ACTUALLY HAPPENING

Five metabolic states. One clock. Most people only ever reach the first two.

Fasting isn't binary. Your body moves through distinct, sequential states — each unlocking a different benefit. Your protocol tells you which ones you're targeting.

0–4h

Fed State

Insulin is elevated, digestion is active, glucose is the primary fuel source. No fat-burning advantage yet.

4–12h

Glycogen Depletion

Liver glycogen stores begin drawing down. Insulin falls. The body starts preparing to shift fuel sources.

12–16h

Lipolysis Rising

Fat oxidation increases as glycogen runs low. Free fatty acids and early ketone production begin.

16–20h

Ketosis

Ketone production rises meaningfully. This is the window most 16:8 and 18:6 protocols are built to reach.

20h+

Autophagy

Cellular cleanup processes upregulate. Extended and OMAD protocols target this zone specifically for longevity.

THE PROTOCOL QUIZ

Five questions. Your exact fasting window.

We'll match your tolerance, schedule and goal to one protocol — 12:12 through OMAD — and hand you a single printable page.

Question 1 of 5
YOUR RESULT

Your personalized fasting protocol.

Print it, pin it, follow it. Recalculate anytime by retaking the quiz.

ZEUTRAL PROTOCOL REPORT

Your Fasting Protocol

Fasting Window
16h
Glycogen depletion → Ketosis
Eating Window
8h
e.g. 12:00 PM – 8:00 PM
Break-Fast Time
12:00 PM
Based on a 8:00 PM last meal
Target Zone
Ketosis
Peak fat oxidation window

Eat when breaking your fast

    Avoid during eating window

      Electrolytes & hydration

        Exercise to maximize fat oxidation

          How to confirm you're actually in ketosis

            Not medical advice

            • This protocol is general wellness guidance, not medical advice. Consult a physician before starting extended fasting, especially if pregnant, nursing, underweight, diabetic, or managing any medical condition.
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