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23:1 intermittent fasting

OMAD means one meal a day. The timer models it as 23 hours without eating and a one-hour window; this is a convention, not a safety recommendation.

23h

Fast

1h

Eating window

Start 23:1 timer

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  • No app
  • No account
  • Not medical advice

By FastWindowTimer · Published: 2026-06-21 · Content updated: · Not individually medically reviewed — see editorial policy

Example schedule

  1. Eating window opens at 6:00 PM

    First planned meal time.

  2. Eating window closes at 7:00 PM

    Last planned meal time.

  3. Fast until 6:00 PM the next day

    23-hour fasting window begins.

Planning considerations

  • A 17:00–18:00 window represents 23:1 on the timer.
  • Use this page to compare timing constraints; suitability requires your own circumstances and, when needed, professional advice.

Practical tradeoffs

Practical use

  • Shows how a one-meal schedule differs from a wider daily eating window.

Constraints

  • One meal leaves little flexibility for adequate nutrition, medication or social eating.
  • Do not alter prescribed medication or ignore symptoms to complete a window.

Sources

  1. Cleveland Clinic — What Is Intermittent Fasting? (opens in a new tab)

    What this source supports: Describes daily time-restricted eating and the weekly 5:2 pattern. The example clock times on this page are arithmetic illustrations. It is background context, not a trial of this exact schedule.

    What it cannot establish: Does not demonstrate that a longer fasting window is better or establish individual suitability.

    Source checked:

  2. Cleveland Clinic — 6 Tips for Fasting Safely (opens in a new tab)

    What this source supports: Discusses planning, hydration, medication and avoiding extreme fasting.

    What it cannot establish: General clinical education, not approval of this exact schedule for the reader.

    Source checked:

Frequently asked questions

Is OMAD a recommended next step after 20:4?
No. Completing shorter fasts does not show that OMAD is suitable. Consider a wider eating window or regular meals and discuss restrictions with a qualified professional.
What does this schedule tell me about my body?
Only the intended eating and fasting times. It does not measure insulin, ketones, autophagy, or the nutritional adequacy of your meals.
What if the schedule does not fit my day?
Choose a wider eating window or regular meal times. You do not need to compensate for a missed target by extending the next fast.

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