Advanced · One Meal A Day
OMAD Calculator
OMAD (One Meal A Day) — the most intense common fasting protocol. Fast for 23 hours, eat 1 large, nutritionally complete meal.
Step 1 — Choose Your Protocol
One Meal A Day — fast 23h, eat 1 complete meal.
Step 2 — Personalise Your Schedule
Your eating window starts from this time
🎯 Your Goal
⏱ Time Checkpoints
Your Fasting Timeline
Elapsed-time checkpoints for a 23-hour schedule. These do not measure metabolic changes.
Fast Started
+0hThe clock measures time since your last calories. It does not measure digestion or metabolic changes.
📄 Mayo ClinicEarly Fasting
+2hDigestion and nutrient absorption vary with the meal and the individual.
📄 NIH — Metabolism OverviewBetween Meals
+4hYour body uses a mixture of fuels. Time alone cannot identify your blood glucose or insulin level.
📄 PubMed — Insulin & Glucose DynamicsOvernight Interval
+8hAn overnight interval may include sleep. Glycogen use varies with diet and activity.
📄 Cahill GF Jr — NEJM 197012 Hours Elapsed
+12hTwelve hours is a time checkpoint, not a diagnosis of ketosis. Ketone production varies between people.
📄 Cahill GF Jr — NEJM 197016 Hours Elapsed
+16hSixteen hours does not establish autophagy activation. There is no validated universal human autophagy timer.
📄 Levine & Kroemer — Cell 2008Time checkpoints are educational, not a recommendation to extend your fast.
OMAD — What You Need to Know
OMAD involves eating all your daily calories in a single 1-hour window. It does not guarantee superior health outcomes and can make adequate protein, micronutrients, and energy intake difficult. Discuss this restrictive approach with a healthcare professional.
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