Intermittent Fasting · 18-Hour Fast
18:6 Fasting Calculator
18:6 takes you deeper into fat burning and autophagy than 16:8. Enter your eating start time to get your exact schedule.
Step 1 — Choose Your Protocol
Intermediate — fast 18h, eat within a 6h window.
Step 2 — Personalise Your Schedule
Your eating window starts from this time
🎯 Your Goal
⏱ Fasting Stages
What Happens Inside Your Body
Live biological stages during your 18-hour fast — each backed by peer-reviewed research.
Last Meal Completed
+0hYour fasting clock starts now. Digestion begins and your body processes the glucose from your last meal.
📄 Mayo ClinicDigestion Phase
+2hBlood glucose peaks and insulin is released. Your body is actively digesting and storing nutrients from the last meal.
📄 NIH — Metabolism OverviewBlood Sugar Stabilizing
+4hInsulin levels begin to drop. Blood sugar returns toward baseline. Your body shifts from storing to maintaining.
📄 PubMed — Insulin & Glucose DynamicsGlycogen Depleting
+8hLiver glycogen stores are running low. Your body begins mobilising free fatty acids as an alternative fuel source.
📄 Cahill GF Jr — NEJM 1970🔥 Ketosis Begins
+12hGlycogen stores are nearly depleted. Your liver starts producing ketone bodies from fat — your brain switches to fat-burning mode.
📄 Cahill GF Jr — NEJM 1970✨ Autophagy Activates
+16hCellular housekeeping begins. Your cells start breaking down damaged proteins and organelles — a key anti-aging mechanism.
📄 Levine & Kroemer — Cell 2008* Biological timelines are approximate and vary by individual. Sources: PubMed, NIH, Cell journal.
Why Choose 18:6?
The 18:6 protocol extends your fast by 2 hours beyond the popular 16:8, giving you more time in ketosis and deeper autophagy activation. With only a 6-hour eating window, most practitioners eat 2 meals per day.
18:6 is ideal for those who have adapted to 16:8 and want to increase the metabolic and cellular repair benefits of fasting without going to the extreme of OMAD.
Medical Disclaimer
This tool provides estimates for informational purposes only. Always consult a licensed healthcare provider before beginning any fasting protocol — especially if you are pregnant, have a history of eating disorders, diabetes, or any other medical condition.
Sources: Mayo Clinic · NIH · PubMed