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OMAD: Too Extreme, or the Best Form of Intermittent Fasting?

OMAD: Too Extreme, or the Best Form of Intermittent Fasting?

Intermittent fasting has been one of the most interesting developments in the health and wellbeing World in recent years. The realisation that limiting your eating to a certain size window each day has proven very successful for losing weight, getting into ketosis, and for reaping the benefits of autophagy. The most common form of IF is 16:8 (16 hours of fasting with an 8 hour eating window), but gradually people have explored shorter and shorter windows in an attempt to amplify the benefits. The logical extension of this process is OMAD – or One Meal A Day.

The OMAD Diet book Alyssa Sybertz

What Is OMAD?

In the simplest terms, OMAD means restricting your eating sessions to just One Meal A Day. As you are eating just a single meal, it has to be quite substantial. In fact, the idea is to cover all the macro and micronutrients your body needs at a single sitting. How long that sitting should be is a matter of some minor controversy, though. The most commonly advocated form specifies a one-hour eating window. Effectively, this makes it a 23:1 version of intermittent fasting. Other forms are even more extreme. Some advocating fitting their entire day’s eating into a period of 45 minutes, or even less.

Personally, perhaps because I am a notoriously slow eater, I lean towards the more relaxed end of the spectrum. That said, when I read of people taking four hours for their eating window, I feel it is hard to define such a regime as OMAD at all. What they seem to be talking about is simply a version of IF but with a slightly longer than normal fasting period.

One Meal A Day book Logan Wolf

What are the Advantages of OMAD?

OMAD comes with a range of advantages. Some of these will depend on your personal preferences and lifestyle. Also, environmental factors will probably need to be taken into consideration. Each situation has its own challenges, limitations, and possibilities. You may be living alone or with a partner. Having to deal with the demands of parenthood may have an impact on your choices. You may be working or not, etc. These will all affect the how and the why of an OMAD diet.

Time Saving

Because you only have to prepare one meal a day, even if that meal is pretty large, the amount of time needed for such processes is much shorter than would be required for more normal dietary patterns. Indeed, some prepare all they need the night before and simply cook it the next morning. The rest of the day is yours to do with as you please. Even washing up time can be shortened by the simple measure of using bigger plates. The whole process of preparing, cooking, eating and cleaning up can easily be completed within a couple of hours, thus freeing up time for the other things you enjoy in life.

No need to Snack

As long as you have created meals that satisfy your dietary needs, there should be no need to snack during the day. Of course, this is intrinsically more the case if you are on a ketogenic or carnivore diet due to the greater satiety value of the foods consumed. The whole process of OMAD will be more difficult on a vegetarian or vegan diet due to the fact that you are only resupplying your glucose stores. Given any reasonable amount of activity, these stores will be depleted within a relatively short space of time.

Those who rely on ketosis rather than glycolysis for their primary energy source have a natural advantage in this area. Ketones can easily supply sufficient energy to last for days, rather than merely hours. Also, given the gustatory effects of eating such huge amounts of fruits and veg at one sitting, you also may not be too popular with your fellow workers following such meals …


Whether following a vegan, keto or carnivore diet, not eating for 23 hours of the day will almost guarantee that you spend a fair amount of time in ketosis. This brings with it such benefits as weight loss and increased insulin sensitivity. There is also much evidence that our brains run better on ketones than on glucose alone (1).


Autophagy literally means ‘self-eating’, though the reality is somewhat less gruesome than the description implies. The self-eating goes on at a cellular level where phagophores will capture and consume cellular debris in order to recycle it or expel it. One can think of it as a kind of cellular housekeeping (2). The body naturally defaults to this self-repair mode once all the processes of redirecting nutrients from the consumption of food has been completed. Hence, if you are constantly eating, as many advocate (some cultures believe in having as many as 7 meals a day), your cells will never get the chance to even start the process of autophagy (or ketosis, for that matter) (3). If this is the case, the cells will gradually become more and more disordered as the cellular debris builds up. This is not a happy state of affairs (4).

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Effects on Hormones: Insulin and HGH

We live in a time when obesity is common. It is everywhere to be seen across the Western world, particularly in the US and the UK. Much of the obesity we see is in no way the fault of the individuals so suffering. Rather, it is the result of the products we are offered as ‘food’ and the encouragement of poor eating habits. Obesity is often the result of hyperinsulinemia and insulin resistance. These need to be controlled if we are to escape its clutches.

The way to do this is to reduce the secretion of insulin. This will lead to our bodies using our fat stores for energy, the process of ketosis, instead of merely glucose. Over time, much like intermittent fasting in general, the practice of OMAD will bring insulin under control. Once this happens, the body will turn more and more to its fat stores as its primary source of energy. A beneficent cycle is thus set up.

Because of its effect of reducing insulin secretion, OMAD will also increase the production of HGH (Human Growth Hormone). This hormone is produced by the pituitary gland. As its name implies, it spurs the growth of children and adolescents. Beyond that, it also plays a key role in regulating body composition, particularly bone and muscle growth, as well as playing a part in sugar and fat metabolism (5). Any form of fasting will tend to increase the production of HGH. In this regard, OMAD represents one more potential string to our bows.

Cognitive Benefits

Due to an ancient survival mechanism, when your body perceives itself to be short of food it will activate the sympathetic nervous system. The perception that you are under threat in some way will result in the release of adrenaline, cortisol and growth hormone. Effectively, you are being readied for action. Many people experience this as increased cognition and a heightened state of awareness (6).

The converse is also true, of course. Being overfed can often lead to post-prandial grogginess. Your body is getting signals to relax. This results in mental slowness, lethargy and a desire to sleep.

Fasting, of which OMAD is a form, can also lead to both neurogenesis and the production of BDNF (Brain-Derived Neurotrophic Factor) (7), (8). Thus, practising OMAD may not only benefit the practitioner in the short term with clearer cognition but may also have significant long term benefits for brain function.

Heart Benefits

From personal experience, I know that heart disease can be a threat to us all. Even if we think we are leading a healthy lifestyle, it can strike out of an apparently clear blue sky. Heart disease is the chief cause of mortality in most of the Western world, and in the world in general. Fasting studies demonstrate that following such routines as OMAD assist in improving heart health (9).

There are many ways in which the OMAD style of fasting may help to improve the health of your heart. It can decrease oxidative stress and inflammation. Such fasting can help improve the health of your mitochondria. It has beneficial effects on levels of triglycerides, insulin, and cholesterol, all of which have an effect on the cardiac system. Both weight and blood pressure are often lowered. Because of the effects on autophagy, cellular health is improved. The list of heart-related benefits goes on and on.

One Meal A Day Intermittent Fasting book by Elizabeth Moore

The Disadvantages of OMAD

Despite the manifold advantages of OMAD, it does come with some problems. Some of these are obvious and simply come with the territory. Others are more subtle and nuanced. Your personal circumstances will have a lot of influence in deciding exactly what form of IF or OMAD is right for you. Indeed, you may even decide that such an extreme dietary intervention is not right for you at all.

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It cannot be denied that restricting meals to just one a day can have social consequences. This is not a trivial problem. Much of social life can come along with the assumption of sharing food. Whether it be a dinner date or sharing a sandwich at work at lunchtime, the expected behaviour includes the consumption of food together. Hence, OMAD can impact aspects of your social life.

Being able to Eat Enough at one Sitting

This is a problem I personally have when trying forms of fasting similar to OMAD, or even OMAD itself. This is perhaps particularly a problem for those of us on keto or carnivore due to the satiating nature of the food we consume. For some of us at least, it can be difficult to force down all the calories we need to keep us going for the entire day in one sitting.


Trying to time your single meal for the day can be problematic in itself. Do you go for an early meal, thus fuelling you for the day but risking feeling quite hungry by bedtime? Alternatively, is it better to go for lunchtime? This may be difficult due to the time it takes to eat a sufficiently large meal, especially if you are working. Is it better to wait until dinner time? The need to eat such a large meal so late in the day could lead to sleep and digestion problems. For many of us, given the demands of our particular situations and environments, the timing of OMAD can present a significant problem.

Insulin Spike

Because we are eating a lot of food in one go, OMAD can lead to a significant insulin spike. This is perhaps more the case if your diet consists of processed foods or even theoretically ‘healthy’ choices such as those available on vegan or vegetarian diets with their reliance on high fructose, hence high sugar, foods. Although those on keto, low-carb, or carnivore will generally be less at risk, there could still be problems in this area.


Some feel that supplementation may be needed for those following OMAD (10). Others would contest this assertion. I know a couple of people who have happily followed an OMAD lifestyle for a decade without any particular need to add anything beyond the content of their meals. Commonly recommended supplements are fish oils, multivitamins, and a range of minerals. Personally, I feel that it is often better to simply rely on a well-constructed diet than to seek answers through supplementation.

Not Ideal For Body Building

This, again, is open to debate. There is much discussion at the moment whether following an OMAD lifestyle is appropriate if one wishes to participate in bodybuilding. Without discussing a host of studies, the general consensus seems to be that OMAD is very good for weight loss and muscular definition, but maybe not so good for the actual building of muscle (11). As ever, the make-up of the meal you consume will make a huge difference. There is an obvious need to ensure an adequate intake of bio-available protein if one’s aim is bodybuilding. Yet another area where those on plant-based diets may suffer in comparison if they are attempting OMAD.

OMAD may not be Advisable for Older People

As with intermittent fasting in general, OMAD needs to be approached with caution by people over 60 (like myself). As we age, it becomes progressively more difficult to utilise our protein intake. One of the chief dangers of this is the threat of sarcopenia. This muscle-wasting condition is a major threat as we pass into our sixth and seventh decades. In order to avoid this danger, we need to ensure that we get sufficient amounts of protein at regular intervals.

Dr Dale Bredensen, the well-known Alzheimer’s expert, recommends that although we should partake in IF as we age, the periods without food should be relatively shorter. In the view of Dr Bresenden, 14 to 16 hours is sufficient to elicit the effects we desire without being overly exposed to the potential risks.

The Keto OMAD Diet by Markus Wilkinson

How To Do OMAD

One of the benefits of OMAD is its extreme simplicity. You eat for an hour or two a day and, essentially, that is it. There are one or two other factors that we may need to consider though.


Exactly when you choose to eat each day is a matter that needs to be addressed. Each possibility has its advantages and disadvantages. Many people feel that the most appropriate time is in the mornings, but this may leave you feeling ravenous as the days goes on. On the other hand, eating too late is not advisable generally and specifically a bad idea if you wish to consume such a large meal. Even when I am not fasting, I generally avoid eating within four hours of my bedtime. Midday may be the ideal compromise but it does all depend on your individual situation. Such matters need to be addressed before embarking on such a drastic lifestyle change.

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Exercise Timing

As a general rule, I like to do my more strenuous resistance training exercise sessions before a large meal. The idea is to take advantage of the stimulation of the mTOR (mechanistic Target Of Rapamycin) pathway that will accompany large intakes of food, particularly carbohydrate or protein. This will help the muscles to repair and recover from the stresses and strains of the exercise session.

On the other hand, if I am doing a bike ride or performing some other form of aerobic activity, I prefer to do this after a larger meal. The idea is to burn off the effects of the glucose boost and get back into ketosis as quickly as possible.

Calorie Intake

It is important to ensure that you take in sufficient calories when you perform OMAD. The idea is not to be pulled into the ancient, and largely discredited, notion of ‘calories in/ calories out’, but to allow your body to enter ketosis and hence burn off fat. Ideally, you should be consuming as many calories in this one meal as you would have done during a whole day’s worth of eating previously (12).

Macronutrient Balance

If we are to attempt OMAD, then care needs to be taken in regards to the macronutrient balance of the meals we prepare. This particularly applies if you are on Keto. It remains wise to keep down the amount of carbohydrate in any given meal. Remember, all these are essentially sugars, at least as far as the body is concerned. Too many carbs and the ensuing insulin spike will be consequently large. Having said that, some of the more extreme proponents of OMAD feel that they can eat whatever they like as the following fasting time will allow the body to deal with any excesses in the diet. This is not a view I subscribe to.

Vitamin, Mineral, and Nutrient Intake

This should go without saying, but try to ensure that whatever dietary habit you adopt, whether it be OMAD, 2MAD or more conventional eating styles, make sure your diet supplies the needed vitamins, minerals, and nutrients. Again, on ketogenic diets this is relatively easy to achieve, though care still needs to be taken. If you are a vegan it may be necessary to consider supplementing for iron, zinc, selenium, DHA, EPA, and Vitamin B12, to name but a few. Apps such as Cronometer and Keto Counter should help in this regard. They are freely available on Android or iPhones.

Fasting Mastery book on OMAD by Harriet Sinclair

OMAD and Keto

The One Meal A Day style of eating and a Ketogenic diet fit together like a hand in a glove. The aim of a ketogenic diet is to create a state in the body where it seeks to rely on ketones as its primary source of energy rather than glucose. Given the short lived nature of glucose based satiation, OMAD will quite naturally lead us toward a state of ketosis. This is especially the case if one does any significant amount of exercise. The combination of the two approaches, consuming a low carbohydrate diet and adopting OMAD, will amplify this effect.

Ketomad book combining Keto and OMAD


Having spent several days researching OMAD, I have come to the conclusion that it is not for me. On the other hand, it is clearly very effective for many people and comes with many advantages. It does require a degree of self-discipline though that not all of us possess. There is an interesting alternative known as 2MAD, or Two Meals A Day. For those of us into our seventh decade or later, such a diet may be more appropriate. As I read the descriptions of 2MAD, I realised that it is essentially the eating pattern I have been following for quite some time anyway. If all goes well, the following blog will cover this interesting adjunct to OMAD. Stay tuned to this station …


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