One Meal a Day (Omad) Diet – The Hardest Form of Intermittent Fasting

OMAD stands for One Meal a Day, also known as a variant of intermittent fasting.

Most people panic at the thought of missing several meals a day. Yet it is the simplicity of this diet that attracts attention: you only eat one meal a day.

This may seem extreme at first because it’s against everything you’ve learned about eating multiple meals in one day. But proponents of the OMAD diet claim many health benefits.

In this article, I examine whether the OMAD diet is healthy and can help with losing weight.

You will also learn the main advantages and disadvantages of this diet, so that you can make the right choice whether this form of fasting suits you.

What exactly is the OMAD diet?

The OMAD diet stands for One Meal a Day, also known as an extreme form of intermittent fasting. With the OMAD diet, you only eat one meal a day and fast the remaining 23 hours of the day.

The periodic schedule of the OMAD diet aims for a fasting ratio of 23:1, giving your body 23 hours every day to enjoy the benefits of fasting.

Most people say you’re crazy if you only eat one meal a day. Yet it’s the simplicity that makes this diet so popular.

You have a small eating window of 1 hour and in that hour you have to get all your calories for that day. You can imagine that this must be a big meal because with only a salad you won’t last long.

This way of dieting is done by people to lose weight quickly. But for people who have never fasted before, this form can be a bit too extreme.

According to proponents of this strict diet, several meals a day keeps our body working unnecessarily.

In fact, there is some historical evidence that the Romans ate only one large meal a day before breakfast began to increase in popularity during the Middle Ages (source).

However, I must add that for people who have never fasted before, this form of fasting can be somewhat extreme (more on this later).

How does the OMAD diet work?

This diet works on the principle that limiting your calories to just one meal a day keeps your body in a constant state of fat burning. The thing is… If you’re constantly eating throughout the day, your body uses those calories at a slow rate to digest food.

As soon as you start fasting, that constant supply of calories falls away. At that moment the glycogen supply (energy from carbohydrates/sugars) will be used first.

After about 12 hours the glycogen supply will be exhausted. Your body will then be forced to use stored fat as a primary source of energy. For fat burning it is therefore important that you fast for at least 12 hours.

Most users who follow the OMAD diet choose to eat their only meal in the evening (so they skip breakfast and lunch). This is also the easiest way to do it, as it allows you to eat with the whole family.

Based on your lifestyle and how you feel, you can experiment with the OMAD diet. Like other forms of intermittent fasting, OMAD is a fairly flexible approach that allows for personal adaptations depending on your preferences.

The number of calories you eat can vary and depends mainly on what your goal is. But normally no calories are counted. Instead, you eat enough to feel full and make sure you take in enough protein, carbohydrates and healthy fats.

In exceptional cases you may take a piece of fruit or a protein shake after an intensive sports session. However, you may drink liquid drinks without calories during the day, such as water, black coffee or green tea.

And what does science say?

A 2016 study found that eating 1-2 meals a day resulted in a significant reduction in participants’ BMI (source).  A 2017 study found that intermittent fasting for six weeks significantly improved both fasting blood sugar levels and body weight in diabetics (source). Studies with a longer research period will have to confirm whether these benefits are valid in the long term.

With intermittent fasting you will be able to lower your insulin values drastically (source). This is beneficial if you want to lose weight and also helps to prevent type 2 diabetes.

Pros and Cons of Omad Diet

The OMAD diet has become popular for several reasons which I will explain in detail below.

In addition to claims for rapid weight loss, further health benefits are granted:

#1: You lose weight

The OMAD diet can be a useful tool because it helps to naturally reduce the amount of food you eat in a day. In our society, the over-consumption of food is inevitable.

On every street corner, you are confronted with food. So it’s no wonder that more than half of the people are too fat. Too much food is just not good.

This is especially true if you have a chronic illness or want to lose weight.

If you decide to follow the OMAD diet, you’ll probably notice that it can still be quite a challenge to put enough calories in a single meal.

In this way you create a natural calorie deficiency and you will lose weight without physical effort. Even if you eat an unhealthy, high-calorie meal (think of a pizza or hair salon), you won’t get as many calories as if you ate all day.

It is also true that ketosis plays a role in losing weight. If you regularly read articles on this website then you are probably familiar with the ketogenic diet. This is an extremely low-carbohydrate diet that puts your body in a state of ketosis and starts burning fat. But the OMAD diet is actually not based on the low carb diet.

In particular, it concerns the depletion of our body’s primary energy source, namely glucose. When we limit carbohydrates considerably, our glycogen supply is depleted. As a result, our body has to be provided with a new source of energy and that is body fat.

#2: it is easy to follow

The nice thing about the OMAD diet is that anyone can start it. You don’t have to read in. All you need to know is that you only eat one meal a day and you skip the other meals.

It makes cooking a lot easier and faster. After all, you only have to make one meal a day instead of two, three or maybe four. You can also prepare a large meal and divide it into portions. Then you don’t have to cook every day.

For some people, this can lead to an increase in productivity because you spend much less time shopping and standing in the kitchen.

What’s more, this diet is so easy to follow that you don’t have to worry about making mistakes. You only eat one meal a day and that’s all!

#3: Autophagy

Another important advantage of this form of fasting is that it stimulates autophagy.

This is a protective process in which old cells are broken down and unwanted waste products leave the body (source, source). 

By eating just one meal a day, you give your digestive system enough time to recover and heal instead of being constantly at work.

Autophagy is a word that goes hand in hand with intermittent fasting. While a more dispersed intermittent fasting schedule can also be successful in promoting autophagy, the OMAD approach can be even more effective because you have a smaller eating window where you can eat.

But the OMAD diet also has some drawbacks:

#1: Can be difficult to get enough calories

A calorie deficiency is necessary if you want to lose weight, but long-term calorie restriction is not good. It is important that you follow a diet that contains enough calories and nutrients to provide your body with energy.

If you only eat one meal a day, it can be quite a challenge for you to get all the food you need at once. A good multivitamin and fish oil supplementation is therefore no superfluous luxury with this diet.

Especially if you naturally have a fast metabolism then this is dangerous because the food you eat burns quite quickly.

If you’ve had an active day, it can be difficult to get all the energy you need from a single meal. This can cause fatigue symptoms and that’s not what you want, of course.

#2: You put yourself full of food

Because people are only allowed to eat a single meal a day, there’s a chance they’ll overeat.

Although some people can digest more food than others, eating a large meal with more than a thousand calories at once will put quite a strain on your digestive system. You may feel bloated, tired, or even sick after consuming so much food at the same time.

There is, of course, something to be said about the kind of food you eat. Your ability to digest the food you eat depends in part on the digestibility of the food you eat. Therefore, eat as much natural and unprocessed food as possible to make your digestion work optimally.

#3: It can be quite a challenge

Eating only once a day can be quite a challenge for many people. In theory it sounds fun, but the reality is that it can be quite heavy. This is especially true for people with an active lifestyle.

If you have a physically demanding job or exercise regularly, this diet is not suitable for you and may even be counterproductive. In the long run, your body will not be able to recover properly, resulting in muscle breakdown and fatigue complaints.

For people who are not very active I say: it may be that after a while your body adapts to this way of eating. This applies of course to every change in your eating pattern. Often people give up too quickly when it comes to eating healthier food.

So although eating just one meal a day may not be the best solution for you to lose weight, I do think you should give everything you try a fair chance.

You can also try fasting once or twice a week, or an even more moderate daily schedule, and build up from there.

But remember that healthy weight loss is gradual and takes time. If you go too fast, you run the risk of losing muscle mass and will quickly return to your old weight (yo-yo effect) as soon as you stop dieting.

#4: You may have some nasty side effects.

Especially if you are used to eating all the time, the complaints are not mild. Chances are that your body is addicted to sugars.

Reducing your sugar intake by fasting is certainly not a bad idea. But quitting sugar can be a bit tricky in the beginning.

The OMAD diet can, therefore, cause unpleasant side effects.

Then you can think of:

  • Concentration problems
  • Headache
  • Feeling nervous
  • Fatigue and little energy

On days when you haven’t slept enough hours, or if you have jet lag, for example, 23 hours fasting is a much bigger challenge. In any case, don’t force yourself to keep fasting if it feels unnatural or uncomfortable.

Experiences with the OMAD diet

The internet is full of sites about the OMAD diet. One says this, the other says that.

Let’s see what other people’s experiences are with the OMAD diet:

It’s now the third week I’ve eaten one meal a day. On the scales I lost 2 kg. I have to say…on the days when I haven’t slept enough, I notice that I am significantly more hungry in the morning. I am often tempted to have breakfast in the morning. Drinking a lot of water has helped me to control my appetite. Whether I’m going to keep this up is still to be seen. – Cindy

When I heard about the OMAD diet I was immediately excited. In the past I’ve done intermittent fasting before. This form of fasting goes a step further. A nice challenge I thought! Now that the first week is over I notice that it is not good for my energy level. I can regularly be found at the gym and now I am often too tired to do my best. I also constantly suffer from an extreme hungry feeling. For my body this extreme form of fasting doesn’t feel good. – Judith

Last month I challenged myself to only eat one meal a day for a week. I have to say I did better than I thought. I was always used to eating 3 meals a day. The first day I felt intense hunger around noon. This hunger lasted for an hour and then fortunately it subsided quite quickly. At 17.00 I ate my only meal. This helped me well to get through the evening. On the second day I felt exactly the same and pulled myself through again. On the third day it went a lot worse. On the way to work my brain was constantly confronted with food and this made me think about food all day long. That’s why I ate my only meal at 3pm. This turned out to be a big mistake. Once at home I had such an irresistible hunger that I ran to the fridge. What I noticed is that a strict routine is very important for this type of diet. If you fall out of your normal routine, you won’t last long. So I quit and am back on a normal low-carb diet. I’ve had good results with that in the past. – Mark

Is the OMAD diet dangerous?

As mentioned before, there are some side effects and possible risks that can occur with this extreme form of fasting.

When in doubt, it is important to contact your doctor before changing your diet and lifestyle.

The OMAD diet can lead to health problems, such as:

  • Fatigue
  • Muscle weakness
  • Insatiable feeling of hunger
  • Brain fog

The OMAD diet can be dangerous for children, young adults and people with diabetes. It is also dangerous for pregnant and breastfeeding women.

Apart from the physical side effects, there are also emotional side effects that cannot be ignored. This diet can make you irritable and lead to other mental health problems.

Conclusion: is the OMAD diet worth a try?

Eating just one meal a day can be a quick solution for some people when it comes to weight loss and improving blood sugar levels. The OMAD diet doesn’t sound that crazy yet. For anyone who is already doing intermittent fasting, it can be the superlative. However, I would like to warn that eating one meal a day is not suitable for everyone.

It’s quite an aggressive way of dieting. That’s why I don’t recommend anyone to eat no more than one meal a day for months at a time. The side effects of this diet should not be underestimated.

In the long term, these kinds of extreme diets can be harmful. The OMAD diet has some advantages, but there are also health risks lurking when the daily calorie intake is limited for too long.

This is not an easy diet that can be sustained in the long term. For this reason, it is not the best approach to sustainable weight loss.

Another drawback of this diet is that the user is basically allowed to eat anything. This is for some people a licence to eat the only meal of the day unhealthy. But you understand that 23 hours of living on an unhealthy meal is not good for your health.

Eating whatever you want sounds very attractive, of course, but you want to balance your only meal a day and make sure it contains enough nutrients.

When it comes to eating healthier and losing weight, you should always be wary of new dietary cravings that present themselves as a simple solution for quick and lasting weight loss.

Personally, I wouldn’t recommend the OMAD diet. It is far too restrictive and can lead to choosing unhealthy foods. If I starved myself all day, I would be more inclined to eat unhealthy, greasy foods than a piece of fish and vegetables.

It is up to you to decide whether this form of fasting is best for your body and your lifestyle. We are all different and what works for one person may not work for another.

If you do want to fast now and then I recommend a much easier way: the 16/8 schedule. I discuss this popular method extensively in my article about intermittent fasting.

With this method, you fix yourself for 16 consecutive hours after which you have a time frame of 8 hours in which you can eat. It is a good way to practice discipline with food and to challenge yourself.

Fan of everything health and fitness related. My mission is to share my knowledge and experience with as many people as possible and help them to find their ideal path to perfect health.