Breakfast, lunch, and dinner. Eating three square meals a day (plus a few snacks thrown in) has become commonplace in modern society.

Many people are eating from the time they wake up until the time they go to sleep. Now, we love food, and aren’t condemning this lifestyle pattern—do what fits you best.

However, there is something to be said about how overconsumption in today’s modern world is leading to diseases that can be linked to either eating too much, too many of the “wrong” foods, or a combination of both. The way we “evolved” to eat isn’t matching up with how modern humans are eating, and this has consequences.

Many people are choosing to take back their health through fasting. Fasting is super popular, and rightly so—it can truly work.

While there are several fasting regimens, one particular iteration, termed one meal a day fasting (OMAD diet) is gaining attention for its “radical” nature. OMAD has been touted as a weight-loss plan, and also as a form of disordered eating. There is a lot to clear up about OMAD.

What is OMAD?

The OMAD diet mandates eating just one single meal each day.

This means that, in most cases, the time period where you’re eating during the day is fit within a 1 - 2 hour window. All of your daily caloric intake is squeezed into this small feeding period, and the rest of the day is spent fasting. In this way, you’re basically following a more “extreme” form of time restricted feeding (TRF) of a 23:1 or 22:2 fasting:eating window.

Doesn’t this sound limiting? Why would anyone want to limit their daily food intake to such a short window? Aren’t there other better, less restrictive ways to fast?

Perhaps, but the powerful benefits of fasting, which at this point are well-supported by science, point to the fact that, when done correctly, the OMAD diet may be absolutely great for some people.

Intermittent fasting (IF) has been shown to benefit many chronic diseases including diabetes, cancer, cardiovascular disease (CVD), and neurological diseases like Alzheimer’s disease.Mattson2017 IF also favors weight loss and reduces risk factors for CVD and other metabolic disorders.Mattson2017

Should you try OMAD? Before digging into the nuances of OMAD, let’s talk about how it differs from other fasting regimens.

OMAD vs. Other Types of Fasting

Intermittent fasting (IF) can involve several iterations. Some of the more popular methods include alternate-day fasting (ADF; where you eat every other day), 5:2 fasting (where you fast for two days of the week and consume food on the other five), or a once-a-week extended fast of anywhere from 24 - 72 hours or more.

What makes IF unique is that it doesn’t necessarily involve a routine or cyclical pattern. IF mixes up the feeding and fasting days during the week. In addition, IF (usually) lets you eat “whatever” you want on the feeding days—what is known as ad libitum eating.

Time restricted feeding (TRF) is an eating pattern that involves consuming food within a preselected window of time during the day, and consuming no calories outside of this window. Typical patterns include a 16:8, 18:6, or 20:4 fasting:eating ratio.

TRF is typically advocated because it is a strategy to align food intake with metabolism and circadian rhythms.

In fact, the food intake of most animals is in line with the light-dark cycle, and TRF is based partially on this theory.Longo2016 For instance, a limited daily feeding window might prevent food consumption during the night, when we might be less optimal at metabolizing food.Longo2016 For example, insulin sensitivity goes down in the evening, and eating at this time might not be as ideal for proper metabolic health.Yoshino2014

So how is OMAD different? While it’s given a special name, OMAD is a form of TRF with a super-short feeding window. With TRF, you may consume multiple meals during your window. With OMAD, however, one meal a day is all you get.

The Origin of Three Square Meals

Fasting is sometimes seen as dangerous, radical, or even a sign of an “eating disorder.” The only real reason for this is because fasting goes against everything we’ve been taught about how to eat, and society doesn’t see it as “normal.”

Whether it’s all-day grazing to “stoke your metabolism” or making sure to eat a big breakfast (because it’s the “most important meal of the day”), our patterns of food consumption have been shaped by recommendations that are largely unfounded (in science, at least). Fasting turns our preconceived notions about eating on their head.

Humans didn’t evolve eating three balanced meals per day. In fact, food scarcity, rather than abundance, was the norm for most of our species’ evolution. A caveman didn’t sit down for breakfast before work, have lunch catered at her desk job, and sit down to a nice family meal for dinner. She could’ve (maybe) got one good meal per day. Involuntary OMAD.

Most of us have never questioned the fact that we sit down to three meals per day whether we are hungry for them or not. It’s societal. Sure, it works well for some, but chronic overconsumption is one of the reasons for the worldwide epidemics of obesity, diabetes, and other modern diseases.Bhupathiraji2016

In fact, there is likely no biological reason to eat three meals per day—as researchers have pointed out.Freedman2007

So where did “three squares” even come from? Well, this cultural eating pattern evolved during the industrial era to fit with the job structure of many people.

Traditionally, factory workers would have breakfast before heading to work or school in the morning, take a “lunch break” in the middle of the day, and have a family dinner.

In the 1920s and 1930s, the U.S. Department of Agriculture (USDA) began to promote breakfast as the “most important meal of the day,” and the lunch break served as a way to sustain workers in manual labor jobs who needed some energy in the middle of the shift.

Times have changed. So have portion sizes. And the type of food we’re eating. This means that our eating structure might need an update.

Most of us wake up still full of energy from last night’s dinner, only to eat a big, calorically-dense breakfast. Then, we go to work and sit at a desk for hours—expending little energy throughout the day. But when lunch rolls around, participation is almost mandatory.

As a result, modern day humans are eating from sun up to sun down. In fact, a study that used a mobile app to monitor the eating habits of adults indicated that over half of the people ate for a time period of over 15 hours each day!Gill2015 The only time they were “fasting”? During sleep.

There are several questions surrounding our current eating patterns? Is our accepted pattern of eating the best way?

Fasting advocates don’t think so.


Even if you’re a regular intermittent faster or have some experience with TRF, you might have some questions or concerns about OMAD before you consider adopting the way of eating.

That’s natural—eating only one meal does go against a lot of what we are told to believe about how we should fuel ourselves. Here are a few questions and critiques (with answers) about OMAD.

Won’t I Be Hungry All the Time?

At first, maybe. Most of us have been eating three meals a day for our entire lives, and our bodies are adjusted to a pretty consistent intake of food throughout the day. Changing up this pattern to eat just one large meal a day is a drastic deviation from the norm.

Not only that, but the body is trained to expect food at certain times of the day. Just like your dog knows when to beg for their kibbles at certain times of the day, our stomach and other organs release signals in anticipation of food consumption—and a lot of these are programmed through years of eating routines.

Starting to eat in a new way will disrupt your usual rhythms, but that’s o.k. While you might feel a few hunger pangs at breakfast or go to bed a bit hungry some nights, you’ll eventually adapt.

Once your body learns to expect one meal per day at the time of your choosing, you’ll likely start to feel hungry around this time—while feeling a lack of hunger at other times of the day.

In addition, if you’re eating one meal a day as part of a high-fat or ketogenic diet, you will eventually become more efficient at burning fat for fuel. Burning fat and ketones, instead of carbohydrates, will result in less hunger—ketones actually have been shown to inhibit hunger hormones like ghrelin.Stubbs2018 You’ll be less hungry, but still have high-energy. Ketogenic diets are also highly satiating, which means you’ll feel satisfied with your one meal a day as long as you eat enough.Benlloch2019

The fear of being hungry is a valid reason to be hesitant about starting OMAD. However, it’s very likely that after a few weeks, your body will adapt to this way of eating, and you’ll likely feel much better than you ever have.

Is it Safe to Only Eat One Meal a Day?

The “safety” concern of OMAD comes from several sources, including the possibility that fasting may cause low blood sugar, low blood pressure, or hormone imbalances.

These are all possibilities—and obviously extended fasting periods are not recommended for some individuals, including pregnant women, teens, or people who may be at risk for eating disorders or nutrient deficiencies.

But, for most people, eating only once per day may have more benefit than risk.

Very few studies on fasting in a clinical or research setting report that adverse events occur in participants. If you’re making the effort to drink enough water (and perhaps add some minerals on an as-needed basis), the risk of hypoglycemia (low blood sugar) or hypotension (low blood pressure) are minor.

As for nutrient deficiencies, these can be offset by ensuring that your one meal a day provides a sufficient amount of macronutrients and calories for your body. Including veggies, healthy fats, protein, and food choices that are nutrient-dense on your dinner plate (or whatever meal your OMAD becomes) can ensure that this diet regimen gives you everything you need.

Many people who adopt OMAD are eating a high-fat or ketogenic (keto) diet, and therefore are prioritizing nutrient-dense foods already.

While you may initially find it hard to “stomach” all your daily calories into one single meal, it will eventually become easier.

Some people on OMAD report easily eating 2000 or more calories in a single meal. With high-fat animal foods and nutrient-rich whole foods, this might not be as hard as it seems.

And if you are concerned about a potential nutrient deficiency on OMAD, there’s always the option of supplementation, especially if you’re an athlete.

A well-planned OMAD eating regimen is likely safe for most people. And, when done correctly, yields several benefits.

Benefits of OMAD

Now it’s time to get into the science of fasting. One important note to make here.

Since OMAD is a pretty “niche” fasting regimen, most studies on fasting have chosen more liberal IF or TRF regimens—there aren’t many research studies on OMAD eating per se.

Nevertheless, fasting physiology is similar, and thus the benefits from fasting studies can be used to infer benefits that one might receive from OMAD — including increased fat burning,


Autophagy is a hot buzzword, but what does it even mean?

In simple terms, autophagy can be thought of a cellular garbage recycling process—whereby damaged or senescent (non-functional) cellular structures are taken up by a packaging unit called lysosome and then degraded and recycled into new cell components.Klionsky2000

By self-digesting damaged cell components, our body can prevent the build up of senescent and dysfunctional cells, which are thought to be one of the causes of aging and disease. Indeed, the process of autophagy is associated with longevity in many organisms.Madeo2010

Unfortunately, there is a lack of autophagy research in humans—it’s a hard process to measure. Some studies in mice have indicated that fasting periods of 24 - 48 hours (24 hours would be similar to OMAD) can induce autophagy in neurons.Alirezaei2010

There is also some evidence to suggest that fasting-mediated autophagy may be a promising therapeutic approach in the treatment of many cancers, though more research needs to be done in this area.Alirezaei2010

So, while we can’t define a specific time period of fasting or a hard “level” of autophagy that might come from eating one meal a day, it is likely that at least low levels of autophagy are being activated by extending your daily fasting window to around 24 hours.


We all want to live longer, right? At least as long as we can maintain our health and robustness.

Well, OMAD and fasting show a lot of promise in the area of longevity. This may be due at least partly to the aforementioned process of autophagy.

In worms, flies, and mice, fasting is known to extend longevity by reducing oxidative damage to cells, lowering inflammation, optimizing energy metabolism, and increasing cellular protection and resistance against stress.Longo2016

All of these fasting-induced pathways delay the aging process, and thus can delay the onset of age-related diseases and promote healthspan as well as lifespan.

Interestingly, one study in mice indicated that once per day feeding may enhance longevity. One group of mice were fed a single meal each day and compared to mice who were fed ad libitum or calorie restricted (CR). The OMAD mice and CR mice both experienced increases in longevity, and this was independent of their diet composition. Even though the OMAD mice ate 30% more calories than CR mice, they experienced similar improvements in lifespan and healthspan.Mitchell2019

It’s hard to do longevity studies in humans, given our long life span. But, looking at the data on fasting in lower organisms shows some promise that fasting may be a robust way to add years to your life...and life to your years.

Brain Health

Research suggests that fasting may have benefits for the brain. Fasting changes the neurochemistry of the brain, bolsters neuronal activity, and might be one way to optimize brain function.

In particular, fasting might affect four regions of the brain; the hippocampus, striatum, hypothalamus, and brainstem. These regions are responsible for cognitive processing, body movements, food intake, and cardiovascular and digestive processes, respectively.

The brain is actually the only organ that does not decrease in size in response to fasting!Longo2014 This is likely an evolutionary adaptation that allowed high-level cognitive function even under periods where food was scarce.

Among the changes that happen in the brain during fasting include enhanced plasticity, increased brain growth factors (like BDNF), growth of new neurons (neurogenesis), increased stress resistance, formation of new mitochondria, and reduced inflammation.Longo2014

Fasting may be potentially great for preventing age-related cognitive decline. For instance, in a mouse model of Alzheimer’s disease, both intermittent fasting and calorie restriction were shown to prevent the age-related decline in brain function.Halagappa2007

Many benefits of fasting for the brain might be due to ketone bodies.

The ketone body beta-hydroxybutyrate (BHB) increases in the human brain in response to fasting.PanJW2000 BHB regulates brain-derived neurotrophic factor (BDNF)—a crucial regulator of growth and protection in the brain.Hu2018,Kim2007,Kim2017 This suggests that fasting (and ketogenic diets) can protect our neurons as we age (or all the time).

By eating one meal a day and extending your fasting window, you could potentially gain many of the fasting-induced benefits mentioned above.

Metabolic and Cardiovascular Health

When we talk about fasting, one of the first things that come to mind are probably weight loss and metabolic health and, in fact, these are some of the most-studied effects of fasting.

Losing some extra weight is one of the main reasons people choose to start fasting—though hardly the only one.

Fasting may show promise as a long-term solution to weight loss maintenance in some individuals. In fact, compared to calorie restriction, fasting is likely much more sustainable in the long term.

Though the number of studies on fasting for weight loss are small, there is evidence to indicate that this eating pattern is beneficial for weight loss in overweight and obese individuals.Harris2018

In addition to weight loss, metabolic factors like insulin sensitivity and glucose metabolism may be improved through fasting—which could benefit diseases like diabetes and the metabolic syndrome. Compared to daily calorie restriction (CR), fasting regimens result in similar reductions in fat mass, insulin, and insulin resistance in overweight adults.Barnosky2014 Some evidence in mice indicates that, even when calorie intake isn’t reduced, fasting may improve glucose metabolism.Anson2003

Intermittent fasting also has several beneficial effects on cardiovascular disease risk factors. Fasting improves blood lipid parameters (cholesterol and triglycerides), inhibits the development of atherosclerosis and plaque formation, reduces inflammation, and lowers blood pressure.Malinowski2019

One meal a day eating is similar to many of the fasting regimens studied above—and may have similar benefits.

The data also indicate that even when calories are kept the same, significant benefits that resemble caloric restriction result from extending the daily fasting window, which might be due to an alteration in the gut microbiome, circadian rhythms, and other physiological functions.Patterson2017


This is one benefit you won’t find described in any research paper, but can only experience for yourself.

One attractive quality of OMAD is the simplicity it brings for some people. OMAD requires less planning, less meal prep, and less “worry” about when, where, and what you’re going to eat. If you know when your one daily meal is going to happen, then that’s the only time you think about food during the day. This frees up a lot of mental space for other things like work, friends, family, and exercise.

But how much time can you really spend on food?

It turns out, quite a bit.

A study done in 2011 found that, on average, Americans aged 15 and older spent about 2.5 hours each day eating or drinking. 11% of those studied reported spending at least 4.5 hours each day engaged in activities related to eating or drinking.

This isn’t a negligible amount of time. Of course, it’s important to engage socially, and food and drink are big parts of our culture. However, if you’re only eating 1 - 2 hours during the day, this could lead to enhanced productivity in other areas of life. This is an often reported finding among people who adopt OMAD.

Another “freeing” aspect of OMAD is the lack of time spent “worrying” about calories.

Most people who eat OMAD only think about getting high-quality and nutrient-dense foods, and forget about how many calories their meal contains. Many OMAD advocates say it doesn’t matter.

As the earlier studies showed, the benefits of fasting might occur independent of caloric intake. No counting here; just fast, eat, and repeat.

Potential Downsides of OMAD

Adopting OMAD doesn’t come without potential risks or caveats.

OMAD isn’t for everyone—nor is any fasting regimen for that matter. People who shouldn’t fast include pregnant women, growing teenagers, those prone to eating disorders, or people who have a BMI that puts them in the “underweight” category. For these groups, fasting may pose more of a risk than benefit.

You also have to see how OMAD makes you feel, both psychologically and physiologically. An extended daily fast, for some, may lead to voracious hunger and the temptation to overeat or indulge when meal time comes around.

Overeating might lead to stomach issues, poor digestion, or “refeeding syndrome;” which involves metabolic and hormonal shifts caused by rapid refeeding after a prolonged fast (though this most often occurs in a clinical setting when calories are fed using a tube).Mehanna2008

If you’re prone to binge-eat following a fast, OMAD might not be best for you and rather, a more moderate TRF regimen may suffice.

It’s also important to recognize that OMAD—all fasting really—is a metabolic stress. While stress is good for us and necessary for growth, too much stress imposed at once can lead to burnout, breakdown, and poor health. If you’re combining OMAD on top of the stress of work, exercise, and poor sleep, it might be too much.

You’re better off introducing OMAD gradually, at a period in your life when you have everything else “balanced out” (is there even such a thing?). The purpose of OMAD is not to stress yourself out. In fact, OMAD adoptees are looking for the opposite: a way of eating that integrates well into their lifestyle and reduces stress.

Obviously, starting OMAD introduces a change to your lifestyle, and this could impact social situations. This can be avoided by planning your one meal around known social events.

Many people choose to eat their one meal at dinner—which allows you to eat with friends or family each day. OMAD is also flexible. It’s not required that you eat at the same time each day, though many people do choose this option.

The great thing about OMAD is that YOU get to choose when to eat. It’s a rigid, yet flexible way of eating.

Starting OMAD

Now that we’ve covered all of the basics and the science, let’s talk about how to start off on your OMAD journey.

Whether OMAD is a drastic shift from eating three meals per day or a more moderate transition from your current TRF/IF approach, it might take some time to get into the groove. Getting comfortable fasting for ~23 hours each day isn’t going to come quickly. Adaptation takes a little time.

The hardest thing, initially, might be the feelings of hunger.

If you were used to eating breakfast and lunch regularly, it’s likely you’ll still feel hunger or cravings at these times of the day, at least until you get used to not eating. Breaking the habits and routines associated with food is the first big step to starting OMAD. Just know this; while you might be hungry, you’re definitely not “starving.”

Something else that OMAD brings is a sense of getting in touch with your hunger, and how your body feels during fasting. Over time, you’ll learn how great you can feel, even without food.

One tip to starting OMAD is to limit carbs—which might involve eating a more ketogenic-like diet or upping your fat intake.

Lowering carbohydrate intake while restricting your feeding window will allow you to burn fat and enter ketosis sooner. This will prevent periods of “low energy” and let you burn fat for fuel throughout your 23 hour fast, and perhaps reduce hunger too due to the appetite-suppressing effects of BHB.

We don’t recommend jumping straight into OMAD if you’ve never fasted before.

Instead, it might be best to gradually wean yourself into longer and longer fasting windows. Start with a 16:8 pattern of TRF, then increase to a 20:4. Eventually, you’ll be a fasting pro and have no problem eating one meal a day. In fact, you may start to feel better than you did on 3 meals.

Remember, OMAD shouldn’t be miserable, and shouldn’t be “punishment.” Make your transition painless by gradually introducing this eating pattern into your life.

A final tip to “ease” the fasting. Coffee (black, or maybe with a splash of MCT oil), tea, and other no-calorie beverages might become your friend throughout the 23 hour daily foodless period. These are all o.k. to consume while fasting, since they don’t contain calories and don’t technically “break” the fast.

Before you start OMAD, it may be best to consult with your doctor or a health professional—just to be sure your “healthy enough” to experiment with this lifestyle.

When Should I Eat My Meal?

This is completely up to you. Everyone will choose to eat their meal at one time or another based on social, personal, and lifestyle factors.

Some may choose breakfast—opting to start the day off with a high-energy meal to power through the day or perhaps to recover from a morning workout.

Dinner might be the most preferred option, since this is a meal typically consumed with others. Eating your OMAD at dinner fits well with many modern day lifestyles.

There may also be a physiological reason to consume your meal in the late afternoon and early evening. At this time of day, if we’re often off work and at home, our parasympathetic nervous system activity (our “rest and digest” system) is dominating—favoring digestion. Consuming food in a less stressful environment might promote better metabolism of whatever you’re consuming.

However, there are also studies concluding the opposite. Consuming all of your calories before 3pm (known as early time restricted feeding or eTRF) actually improves insulin sensitivity, blood pressure, and oxidative stress more than a later feeding period.Sutton2018

eTRF has also been shown to reduce appetite and increase fat oxidation compared to a TRF regimen where eating ended around 8 pm.Ravussin2019 The benefits achieved with an earlier feeding window might be due to the fact that insulin sensitivity is highest in the morning. To maximize the metabolic benefits of OMAD, therefore, eating earlier may be ideal.

Since there is evidence for both early and later consumption of food—the decision ultimately comes down to what works best for your lifestyle, and what you enjoy.

Become a Fasting Pro

OMAD is a perfect representation of the ethos of biohacking, taking control of your physiology and psychology by using evidence-based strategies.

Rather than allow it to run on social cues, you can tell your own body how to act, and how to perform. Fasting changes physiology for the better. In addition to all of the amazing health benefits that fasting has for the body, it also introduces a new way of eating that many people find empowering.

OMAD is a lifestyle that, far from a fad, is becoming the normal way of eating for many. Give it a try, and see how you feel.

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