OMAD Diet: is it advisable to eat one meal a day?

OMAD Diet: is it advisable to eat one meal a day?

Do you know about the OMAD diet? Is eating only one meal a day healthy?

We’re going to answer that question from a scientific point of view. Don’t miss out!

What is the OMAD diet?

The OMAD diet, standing for “One Meal A Day”, is an advanced intermittent fasting method that calls for having only one meal a day.

What is the OMAD diet?

Although the OMAD diet is its better known name, we could also call it simply a 23:1 intermittent fasting protocol.

Which means 23 hours of fasting a day and a very restricted eating window of only 1 hour.

How to follow the OMAD diet

The OMAD diet is normally an advanced progression of more moderate and reasonable intermittent fasting protocols

Generally, someone would start by experimenting with 16/8 intermittent fasting, reducing their 3-5 daily meals to only two.

With time, they might want to reduce this eating window even further, from 8 hours a day to only 6, or even 4.

We would therefore already be in a 20:4 protocol, which is quite close to the OMAD.

One single meal

Later on we’ll discuss why this protocol is not suitable, or even recommended, for a large part of the population.

The OMAD diet would only be step even further, in which you consume one large daily meal and fast the rest of the time, being able to consume caloric liquids during the fasting hours.

What foods can I eat?

With the OMAD diet being an intermittent fasting diet, it doesn’t prescribe foods as such.

However, you do have to bear in mind certain notions and rules that will help you avoid medium-term problems if you’re going to follow such an extreme protocol.

The first point to pay attention to would be:

Your micronutrient consumption

  • When having just a single meal, the micro (and macro) nutrients that you previously distributed across 3 or 4 meals have to be included in just one.

If you don’t, and opt for example to include a limited variety of foods, you might end up with deficiency if you keep up the protocol for a long time.

This would be solved by including a good portion of varied vegetables in your meal.

The second point is just as, if not more, important than the first:

The amount of protein you include in your diet

  • Both for those looking to lose weight and those looking to maintain it, and especially if you’re an active person, it advisable not to lower your protein intake of 1-1.2 g/kg weight per day.

This means that if you weigh 80 kg, you should consume at least 80-90 grams of protein in your single daily meal.

One meal a day

For many people, this could be an issue, not being able consume so much (along with the rest of the macronutrients we need).

We’re talking about the equivalent of 6-7 medium sized eggs or 400 grams of chicken.

The final point to mention is relative to:

The total calories

  • That’s to say, the energy you’re consuming in your one meal.

If you want to lost fat, it’s clear that creating an energy deficit at a short-medium term is going to help you, and the OMAD diet might guide you in this direction.

OMAD the diet to lose fat

The problem lies when this energy deficit is too great and we maintain the diet for a long time.

Here the clinical problems begin, which taken to an extreme could include amenorrhea, loss of bone mineral mass, muscle loss, accentuated hair loss, among other symptoms.

Benefits of OMAD

That said, there are benefits of this extreme intermittent fasting protocol that we can highlight.

It’s clear that it contributes to weight loss and fat loss in the majority of people (see next section), but apart from this much sought-after effect, some people report that it improves previous gastrointestinal symptoms, both mild (dyspepsia, bloating, colic) and the more severe..

In this case we are moving into the field of anecdotal evidence:

  • There are no clinical investigations or systematic reviews of OMAD.
  • Though there are of other similar intermittent fasting protocols .

The rest of the benefits attributed to the OMAD diet are relative to the weight loss achieved, including:

  • Improved insulin sensitivity.
  • Decrease in blood pressure and inflammatory parameters.
  • Reduction of visceral fat %.
  • Lower cardiovascular risk.

Can I lose weight eating one meal a day?

If you tolerate OMAD well, you can benefit from it in the short term: The most obvious benefit being fat loss.

It’s easy to explain:

  • The average person has 4-5 daily food intakes to cover the necessary daily calories. This means between 28 and 35 opportunities for intake per week.
  • On the OMAD diet, these opportunities would be limited to 7, which would greatly limit that person’s energy intake if we don’t make a titanic effort to eat the whole fridge when it’s time to eat.

Healthy diet

In the same way, if the average person has to consume 2000 kcal per day, it’s much easier to do so in 3 or 4 meals than in just one.

This is for physiological reasons, because if we are not properly trained (see competition eaters) our satiety at a central level and at a gastric capacity level will greatly limit this single food intake.

This ultimately results in a caloric deficit that can range from 30 to 60% compared to a basal intake, and a weight loss that will be the consequence of that energy deficit.

Contraindications and risks

Being an advanced intermittent fasting protocol, the contraindications of intermittent fasting obviously also apply to the OMAD diet, and they may even intensify.

I’ll remind you that it is a bad idea to follow any intermittent fasting protocol, in general terms (there are exceptions), for those who:

  • Are of extreme ages: children and the elderly
  • Are pregnant and breast-feeding
  • Have a history of eating disorders
  • Have serious and advanced diseases (cancer, advanced renal or hepatic insufficiency, etc.)
  • Are polymedicated and fragile patients
  • Are patients on anti-diabetics or insulin, without making dosage adjustments
  • Have clinical needs for a fractionated diet, which happens in various conditions.

Can I follow the OMAD diet?

Like all diets, it has to be programmed to get you closer to your goals while avoiding nutritional deficiencies and undesirable effects in the short and medium term.

These undesirable effects will become more frequent the longer you eat only once a day, but they are rare if you want to experiment with it for a few days or weeks.

If you don’t find yourself in any of the above categories and want to try the OMAD protocol, I recommend you seek the help of a nutrition professional before starting.

What the science says

There is no scientific evidence on the OMAD diet yet.

The most similar protocol evaluated in clinical trials is that of fasting on alternate days: an ad libitum intake (without restrictions) is carried out alternating with 24h fasting, which can be total or partial (providing 20-25% of the maintenance kcal).

The available scientific evidence tells us that this intermittent fasting protocol (called ADF) is an alternative for weight and fat loss, and has no major side effects, but has significantly less adherence than other more moderate protocols (Heilbronn et al., 2005) (Trepanowski et al., 2017)(Stekovic et al., 2019).

This is perfectly understandable, as a society we’re not prepared to eat only one meal a day, and in the majority of cases (not all) it’ll be counterproductive.

Keto Diet and OMAD

Another “hot topic” in nutrition is the union of the well-known ketogenic diet and the OMAD protocol.

In this case, the complexity of the diet increases, and it is essential to have the diet programmed by an expert to avoid any problems.

Why? The ketogenic diet is a restrictive diet per se (limits several food groups), as well as anorexigenic (reduces appetite).

If we add to this a single opportunity for food intake, it’s easy to incur in the medium to long term the previously mentioned problems: amenorrhea, osteopenia, irritability, relative energy deficiency syndrome, low libido or decreased performance, to mention a few.

OMAD and keto diet

This isn’t to say that there aren’t individuals who would benefit from a short term union of a keto diet and an OMAD diet; in fact, in some respects it would establish certain synergies.

For example, the reduced appetite caused by ketone bodies would help you better tolerate the hours of fasting.

OMAD Diet Menu

A well-planned OMAD diet menu aimed at a person of 75-80 kg could be the following:

Recipe Tips: OMAD Diet Menu

  • Preparation time: 15 minutes
  • Cooking time: 20 minutes
  • Portion size: 1 Plate
  • Number of servings: 1
  • Cooking style: American


  • A handful of green leaves
  • 80 grams of mozzarella
  • 50 grams of olives
  • 1 avocado
  • 1 tin of mackerel
  • 1 pomegranate
  • 1 mango
  • 30 grams of chia seeds
  • 2 eggs
  • 1 sweet potato
  • 300 grams of pork fillet
  • 1 Greek yoghurt
  • A handful of frozen blueberries
  • 1 tablespoon of honey
Nutritional Information per serving
of which saturates:23,8g
of which sugars:68,6g

How to make: OMAD Diet Menu

  1. Heat the oven, while doing the same with a frying pan with a little olive oil.
  2. Cut the sweet potatoes into fine strips. Place in an oven dish and add salt and pepper.
  3. Put in the oven at 180º for 15min.
  4. Cook the fillet over a low heat.
  5. Beat the eggs and cook the Spanish omelette.
  6. Prepare the salad: add the green leaves and the rest of the ingredients – cheese, avocado, olives, seeds, mackerel, pomegranate and mango – to a bowl.
  7. For the dressing, oil, vinegar and salt.
  8. Serve.
  9. Dessert: mix the Greek yoghurt with the blueberries and honey


  1. Heilbronn, L. K., Smith, S. R., Martin, C. K., Anton, S. D., & Ravussin, E. (2005). Alternate-day fasting in nonobese subjects: Effects on body weight, body composition, and energy metabolism. American Journal of Clinical Nutrition.
  2. Stekovic, S., Hofer, S. J., Tripolt, N., Aon, M. A., Royer, P., Pein, L., Stadler, J. T., Pendl, T., Prietl, B., Url, J., Schroeder, S., Tadic, J., Eisenberg, T., Magnes, C., Stumpe, M., Zuegner, E., Bordag, N., Riedl, R., Schmidt, A., … Madeo, F. (2019). Alternate Day Fasting Improves Physiological and Molecular Markers of Aging in Healthy, Non-obese Humans. Cell Metabolism.
  3. Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, K. K., Gabel, K., Freels, S., Rigdon, J., Rood, J., Ravussin, E., & Varady, K. A. (2017). Effect of alternate-day fasting on weight loss, weight maintenance, and cardioprotection among metabolically healthy obese adults: A randomized clinical trial. JAMA Internal Medicine.

Related Entries

  • Everything you need to know about Intermittent Fasting in this link.
  • Do you know about the Ketogenic Diet and its Benefits? Find out now!
  • It’s not secret that to lose fat you need to consume less calories that you burn… continue reading.
Review of OMAD Diet

What it is - 100%

Benefits - 100%

Contraindications - 100%

Example menu - 100%


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About Borja Bandera
Borja Bandera
Borja Bandera, a young doctor dedicated to the areas of nutrition, exercise and metabolism, combines his clinical activity with his vocation for dissemination.
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