OMAD takes intermittent fasting to its most extreme point: one meal, roughly a 60-minute window, and 23 hours of fasting. It is the most restrictive fasting schedule on this site, and the evidence behind it is thinner than most people assume.

Most Extreme Fasting Schedule
Very Limited Human Research
Not Recommended Without Medical Guidance

Medical disclaimerOMAD is the most restrictive fasting pattern we cover. It is not appropriate for everyone and can raise cholesterol and blood pressure in some people. Talk to a doctor before trying it, especially with any cardiovascular risk factors.

Quick Facts

Fasting Window~23 hours
Eating Window~1 hour
Human StudiesOnly one small trial (11 participants, 11 days)
vs. 16:8Far more restrictive, weaker evidence base

How the Evidence Compares

General intermittent fasting for weight lossModerate to strong, well-studied at less extreme windows
OMAD specifically, in humansVery weak — essentially one small short-term trial
OMAD raising LDL cholesterol and blood pressureDocumented in the available short-term data

The Real Risks

Fiber and micronutrient shortfalls

One meal makes it very hard to hit 25–30g of daily fiber and full micronutrient needs. Prioritize vegetables and a wide variety of foods within your single meal.

Blood pressure and cholesterol changes

Documented in available research, even in healthy adults. Get baseline bloodwork before starting and monitor if you have any cardiovascular risk factors.

Rebound eating and yo-yo patterns

Returning to normal eating after extreme restriction commonly leads to rapid regain. Have a clear plan for how long you intend to follow OMAD, not an indefinite one.

Hormonal effects

Some women report menstrual cycle disruption on extreme fasting schedules. Stop and consult a doctor if you notice cycle changes.

Who Should (and Shouldn’t) Try This

Consider If…Experienced With Fasting

You’ve already succeeded with 16:8 and 18:6 and want to test a more extreme window short-term, ideally with medical guidance.

Avoid If…New to Fasting

Jumping straight to OMAD without building up through less extreme windows first is a common mistake and unnecessarily hard.

If OMAD feels too extreme, our fasting schedule comparison covers gentler options with a much stronger evidence base.

FAQ

Is OMAD safe?

For most healthy adults it is not considered dangerous short-term, but it can raise blood pressure and LDL cholesterol in some people and is not recommended without medical guidance, especially with any cardiovascular risk factors.

Does OMAD work better than 16:8 for weight loss?

Not necessarily. It creates a similar calorie deficit through a more extreme restriction, but research does not show it produces meaningfully better weight loss than less extreme fasting windows.

Can I eat anything I want during the one meal?

Some versions of OMAD allow this, but it works against getting adequate nutrition. Prioritizing protein, fiber, and micronutrient-dense food in that single meal matters more on OMAD than on any less restrictive schedule.