Is OMAD the same as 23:1 fasting?

Yes. OMAD stands for one meal a day, which works out to roughly 23 hours of fasting and a one-hour eating window.

Is it safe to eat one meal a day?

It depends on the person. Some healthy adults do it without problems; for others it is a bad fit. It is not suitable for people who are pregnant, under 18, or managing certain health conditions. Ask a doctor if you are unsure.

What can I drink on OMAD?

Water, black coffee and plain tea during the fast. Drinking enough matters more on long fasts.

OMAD and 20:4 fasting: how one meal a day works

The longest daily plans. They are simple to describe and demanding to do, and they are not a starting point.

Short answer

OMAD means one meal a day: you fast for about 23 hours and eat within one hour (23:1). 20:4 is a step shorter, with a 4-hour eating window. Both are advanced plans for people already comfortable with 16:8 or 18:6.

OMAD vs 20:4

20:4: a four-hour window, usually one large meal and a smaller one or a snack, for example 3:00 pm to 7:00 pm.
OMAD (23:1): one meal, eaten at about the same time each day, most often dinner.

The practical difference is whether you get a second chance to eat. 20:4 is far more forgiving, and it is the sensible step between 18:6 and OMAD.

What to expect

The meal has to carry a full day of nutrition, so it needs to be large and varied.
Afternoons are the hard part. Water, black coffee or plain tea help.
Energy for training can drop. Many people keep hard workouts close to the meal.
Social meals outside your window become a choice between the plan and the table. Choosing the table is fine.

Who should skip OMAD

Long daily fasts are not recommended if you are pregnant or breastfeeding, under 18, underweight, have diabetes or take medication that must be taken with food, or have any history of disordered eating. If you are unsure, ask a doctor before trying it.

How to work up to it

Be comfortable on 18:6 first.
Move to 20:4 and keep it for a few weeks.
Try OMAD on one or two days a week before making it daily.
If you feel faint or unwell, eat. Go back to a shorter plan.

How to track OMAD or 20:4 with Bide

Long fasts are where a clear timer earns its place.

Choose 20:4 or 23:1
Both are presets in the plan picker, labelled Warrior and OMAD.
Follow the stages through the day
The ring has a marker for each stage, so a 20-hour fast is broken into parts you can tick off.
Log water as you go
The water card sits on the same screen as the timer. One tap adds 250 or 500 ml.
Check in when you finish
Record how you felt after each fast. Over a few weeks the moods show whether the plan suits you.

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Common questions

Yes. OMAD stands for one meal a day, which works out to roughly 23 hours of fasting and a one-hour eating window.

Sources

The studies and health guidance this guide draws on.

A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adultsAmerican Journal of Clinical Nutrition, 2007
Effects of four-hour and six-hour time-restricted feeding on weight and cardiometabolic health: a randomized controlled trial in adults with obesityCell Metabolism, 2020
Effects of Intermittent Fasting on Health, Aging, and DiseaseNew England Journal of Medicine, 2019

This guide is general information, not medical advice. Talk to a doctor before fasting if you are pregnant or breastfeeding, under 18, have a health condition or take medication.

Short answer

OMAD vs 20:4

What to expect

Who should skip OMAD

How to work up to it

How to track OMAD or 20:4 with Bide

Choose 20:4 or 23:1

Follow the stages through the day

Log water as you go

Check in when you finish

Common questions

Sources

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