Everything you need to know about the OMAD diet

Written by Aly Owen

Medically reviewed by Josie Porter, RD

The “one meal a day” (OMAD) diet is a type of time-restricted eating intermittent fasting schedule that involves — you guessed it — eating just one meal a day and fasting the rest of the time. Whether you choose to eat breakfast, lunch, or dinner, the process is the same: eat all the nutrients you need for the day in one meal and fast for the next ~23 hours. 

Eating one meal a day in a safe, effective way involves serious planning and preparation (think careful meal plans and being very mindful of your hydration levels). 

Plus, like any food routine that involves more than 20 hours of fasting, we strongly recommend speaking with your doctor and having them review your plan to see if this type of fasting schedule could work well for you. 

To help you understand more about what the OMAD diet is, how it all works, and why it may or may not be a good fit for your unique body and health goals, our experts have outlined everything you need to know about eating one meal a day. If you’d like to brush up on the basics of intermittent fasting first — and learn about the other types of time-restricting eating schedules — you can also check out our guide to intermittent fasting for beginners. 

What is the OMAD diet? 

Remember that time you pushed through back-to-back meetings and lived off cups of coffee until dinnertime? Or when you had breakfast with your family but then spent the rest of the day shuttling the kids around and running errands until you fell asleep on the couch that evening? Or maybe even when you slept in, got up for an early lunch, but then decided to retreat back to bed to watch Netflix and nap until the next morning? (That last one actually sounds pretty great, not gonna lie … )

Before we get too distracted by the fantasy of an uninterrupted 8–10 hours in bed, the point is that most of us have had those days where we unintentionally only end up eating one meal. Intermittent fasting OMAD involves doing that same thing — but with more mindful intention and planning. 

So, exactly what is OMAD, and what is the OMAD diet all about? 

Later, we’ll get into the specifics about what that one meal might actually look like, but the basic OMAD diet schedule is built around eating one meal (or one meal plus some light snacks) over the course of an hour (maybe two) and fasting for the rest of the day. That means you’ll be fasting for 22–23 hours and meeting all your daily nutritional needs — through nutrient-dense, minimally processed foods like whole grains, fruits and veggies, lean protein, and healthy fats — during the course of that one-meal eating window. 

The one meal a day diet differs from other intermittent fasting schedules in its level of fasting requirements. For example, other time-restricted intermittent fasting schedules, like intermittent fasting 16:8 or the Warrior Diet, are based on longer eating windows and shorter fasting windows. Likewise, the 5:2 diet, alternate-day fasting, and Eat Stop Eat intermittent fasting schedules involve some strict fasting, but only on certain days; the rest of the time, you eat as you normally would. 

As a highly restrictive form of intermittent fasting, OMAD isn’t for everyone, and like with any food routine, finding one that works for your body and your lifestyle is critical. 

If you’re considering an OMAD schedule, we recommend consulting your doctor first to see if it might be a safe, effective approach for you (especially as we don’t recommend trying any fasting approach where you go 18+ hours without food or with only limited calorie intake). You can also take our Simple quiz to find out if and how intermittent fasting, in general, might help you achieve your health goals.

What does the research say about OMAD? 

Although there is a lot of evidence that associates intermittent fasting — especially time-restricted eating — with weight loss,[1] reduced body fat,[2] lower systolic blood pressure,[3] reduced inflammation,[4] and general metabolic health,[5] there isn’t much research that focuses specifically on how an OMAD fasting schedule affects health and whether any potential OMAD benefits would be short or long term.

While a few studies suggest eating one meal a day results in lower overall body mass [6] and lower fat mass,[7] these studies are limited by small study samples, often with healthy individuals and short durations. Likewise, there isn’t any evidence to suggest more fasting or longer fasting windows could provide more benefits. 

In other words, “more” isn’t necessarily “better,” so you may get the same results with less restriction. And life is hard enough without making it tougher on yourself! 

When it comes to any fasting-based food routine, one important bottom line to remember is that everybody is different, and not everyone will experience the same (or any) benefits of intermittent fasting. 

That’s why it’s important to have a clear idea of what your goals are — why you’re trying out intermittent fasting in the first place — and be very mindful of and kind to your body in the process so you can make necessary adjustments as you go. Your body is there to support you, so you want to support it right back by giving it what it needs to thrive.

So, how does OMAD work? 

Like other intermittent fasting schedules, one meal a day fasting works by using a timed eating break to get your body into a state that helps you shed fat and gain energy.

After you chow down, your body gets to work on digesting and sifting through all the food you just ate for the nutrients it needs. To do that, it phones a friend — insulin — to take those nutrients where they need to go. Over the next few hours, your body transforms your meal into stuff like energy, fat, muscle, and brain power before entering its couch potato phase — the 8–12 hours of post-feast contentment. 

Finally, about 12–14 hours after your last meal, your body enters a fasted state, where it’s ready to burn fat to use as its fuel. 

On a typical day, you probably won’t go more than 12 hours without eating, and following an OMAD diet schedule means intentionally extending that fasting period to a whopping 23 hours before you eat another meal. 

Although the fasting component of the OMAD plan is very restrictive, here’s the good news when it comes to the eating window: instead of focusing on what you eat, this food routine is driven by when you eat. So, rather than meticulously counting macros or measuring portion sizes, you just have to keep an eye on the clock. This structure is especially helpful for those of us who hate counting calories (or have an inherent fear of numbers, thanks to a particularly terrifying ninth-grade algebra teacher).

However, as thrilling as it may be to inhale whatever you want for an hour a day, you will need to manage both your fasting and eating windows carefully to ensure you’re getting all the nutrients you need. That means some pretty attentive meal planning. 

What to eat on the OMAD fasting schedule 

Not sure what a one meal a day plan might involve? While your specific strategy for how to meal plan should be based on your individual needs and lifestyle, there are a few key steps to follow if you’re planning to use the OMAD framework. 

We’ve put together some advice on what to eat during intermittent fasting and what you can drink while fasting, but broadly speaking, you want to make sure your meals are high in lean protein, as protein is essential for building and maintaining muscle mass.[8] So, especially if you’re vegan or vegetarian, make sure you’re prioritizing plant protein — like protein powders, tofu, and beans — and not just carbs!

While food is never inherently “good” or “bad” for you — and you should enjoy your favorite foods without judgment or guilt trips — you primarily want to build meals around foods that are health promoting, nutrient dense, and minimally processed. Good items for your shopping list include: 

• lean protein (like fish, beans, lentils, poultry, eggs, and tofu)
• whole grains (like oats, bulgar wheat, barley, and quinoa) 
• raw produce (fruits and veggies)
• dairy products (like yogurt and cheese) or calcium-fortified alternatives (like almond milk)
• healthy fats (like avocados and nuts)

You also want to keep in mind that hydration is super important for safe fasting, so stock up on zero-calorie beverages like coffee and tea (though we recommend limiting diet soda to two per day since science isn’t sure how large amounts of the stuff affect you long-term). Anything that can make water more interesting — like mint or slices of fresh lemon — is also really welcome when you’re working your way through all those glasses. 

One meal a day (OMAD) and weight loss 

You might be thinking about giving OMAD a trial run for lots of reasons. Maybe you’re looking for ways to boost your energy or improve your metabolic health. Maybe you’ve enjoyed other types of time-restricted eating schedules and want to see what this one’s about. Maybe the thought of planning several meals a day sounds like way too much effort. 

Your reasons are your own, and we’re not here to judge. If you’re considering OMAD for shedding pounds, though, keep in mind that intermittent fasting, in general, has been linked to weight loss (at least in the short term),[9] but there still isn’t much research into specifically whether one meal a day benefits weight loss — or if it would lead to long-term, lasting results. 

Furthermore, intermittent fasting isn’t necessarily more beneficial than a calorie-restricted diet for weight loss,[10] and it may not lead to weight loss without other lifestyle changes [11] (though some studies suggest fasting may be slightly more beneficial for certain aspects of weight loss).[12] 

However, if you’re eating only one meal a day, you are more likely to eat less — at least in volume — than you normally would, and fewer calories means a calorie deficit, which subsequently means potential weight loss. 

On the other hand, restricting your eating window to about one hour can increase those hunger pains (or hangry grumblings) [7] and might make you more inclined to go overboard or choose craving-satiating foods high in fat, sugar, and sodium when you do eat. 

So, while there is some evidence to support the idea that an OMAD routine may lead to weight loss, a lot more research is needed to understand exactly how effective it might be, especially under different conditions and timespans, and how it might affect different people. 

If you’re wondering if you can find your happy weight with OMAD, our Simple quiz may be a helpful place to start your research! 

Can you exercise on OMAD? 

While you can generally still exercise on an OMAD plan, it can be tricky to manage safely. Too much exertion without the proper fuel in your body can be dangerous or, at the very least, leave you feeling sluggish or overly tired and more prone to craving-driven food choices. 

If you’re looking to build physical activity into your OMAD schedule, you’ll need to be extra careful about getting all the nutrients you need during your one meal — and staying extremely hydrated before, during, and after whatever activity you do, no matter the intensity.  

Likewise, you want to understand what your goals are. While physical activity during a fasted state may, in some cases, lead to better metabolic flexibility [6] and more fat burning,[13] it may not be appropriate for endurance training [14] or building muscle mass.[15] 

Above all, you want to listen to your body closely: “No pain, no gain” is not necessarily a good intention to set when you’re starting from a fasted state. Take it slowly, check in with yourself often, and know your limits. It’s totally fine if you’re someone who needs a snack before a stroll, much less an intense cardio moment. 

Health benefits and risks of OMAD 

Your body is your body. How do you know how an OMAD eating routine will affect you specifically?

There are so many different variables involved in a person’s health — like age, lifestyle, health conditions, and physical activity levels, to name a few. This means that some intermittent fasting benefits we see in studies may not always translate to everybody. 

Plus, existing science doesn’t extensively answer the question, “Is one meal a day healthy?” specifically compared to other intermittent fasting schedules. 

The short story: it’s complicated.

But the good news is that we’ve rounded up the science about how intermittent fasting may affect your health and well-being, so you don’t have to. The findings may not be a guarantee for your body or predict how your body might react to the OMAD approach, but they can help you know what to expect.

Health benefits of OMAD 

Lower inflammation 

Inflammation contributes to many chronic and acute illnesses, like high blood pressure and heart disease. Some studies have linked intermittent fasting to reducing inflammation,[4] which may reduce our risk of inflammatory diseases such as type 2 diabetes. These findings may be more likely for those living with overweight and obesity.

Lower risk of type 2 diabetes

Intermittent fasting can improve insulin sensitivity,[16] reduce insulin resistance,[17] and decrease both cholesterol and blood sugar [18] for individuals living with overweight and obesity — all of which are factors that can lower your risk of developing type 2 diabetes and generally improve your metabolic health.

A healthier heart

By lowering inflammation, cholesterol, blood sugar, and insulin resistance, intermittent fasting may also support our cardiovascular health,[19] potentially reducing our risk of heart disease and stroke.

A healthier brain

Some studies suggest that intermittent fasting can promote cognitive performance,[20] stronger, more durable brain cells,[21] and healthy brain aging.[22]

Health risks of OMAD

Hormonal changes

Some research suggests that assigned-at-birth men and women may respond differently to intermittent fasting because it may decrease certain reproductive hormones while not affecting others.[23] A reduction in androgens (such as testosterone) could be beneficial for women with polycystic ovarian syndrome but detrimental to men. However, existing research is very limited and fails to explore the effects of fasting specifically on trans men and women, nonbinary people, and individuals currently on hormone replacement therapy.

Mood changes 

While some studies suggest intermittent fasting may reduce symptoms of anxiety and depression,[24] others also suggest it could increase negative emotions and decrease positive emotions.[25] When you initially start fasting, you may also be more likely to feel hungrier, crankier, or grouchier. But don’t worry! You won’t be hangry forever. After a few weeks, these feelings will pass, and you’ll be enjoying all those intermittent fasting health benefits.

Decreased concentration

Your brain needs certain nutrients from food to function and perform cognitive processes.[26] Following a fasting-based food routine can lead to depriving your brain of these nutrients if you aren’t careful in planning your meals. 

Higher risk of disordered eating 

Intermittent fasting helps bring more conscious awareness to your eating habits and what you eat. While this mindful focus can be a helpful motivator for people looking to introduce more nutrient-dense foods into their routines, it can also lead to disordered relationships with food or exacerbate disordered eating tendencies.[27] This is why we always emphasize that fasting is not suitable for anyone with a history of disordered eating.

Is eating one meal a day safe? 

Is OMAD healthy for everyone? The short answer is “no,” and we recommend speaking to your doctor before starting any fasting method or changing how you eat. You should be particularly cautious, however, if you: 

• are pregnant, breastfeeding, or trying to conceive; 
• have a history of disordered eating;
• have diabetes or another chronic medical condition;
• have poor or irregular digestion; 
• are extremely active;
• have a BMI <18.5;
• are under 18 or 80 years or older; or
• are taking prescription medication (for example, anti-hypertensives, diabetes medications, or any that need to be taken with food).

Even if you don’t fall into any of these categories, you will need to plan your OMAD approach carefully and intentionally to make sure you’re getting enough nutrients and not neglecting anything your body needs.

Pros and cons of the OMAD diet 

Pros 

The benefits of one meal a day are pretty straightforward. With a set eating schedule (one meal during one hour of the day followed by a 23-hour fast) and clear guidance on what foods to prioritize and what foods to avoid in order to maximize nutritional benefits, an OMAD schedule is fairly simple to follow (in theory). 

It also doesn’t require specialty foods or elaborate kitchen set-ups and gadgets, so your shopping bills won’t increase either. In fact, they’ll probably decrease since you’ll be buying for fewer meals. Quite possibly the most appealing pro, though, is that you get to indulge in a super large helping of whatever one meal you choose.

Cons 

While you can, to some extent, eat what you want during your one-meal eating window, you still need to plan your meal very carefully to meet your daily nutritional needs. Since you’re only eating one meal a day, an OMAD routine can also be difficult to manage around social events, school or work schedules, and other life commitments, especially with respect to physical activity. 

One of the main drawbacks of OMAD, though, is that this eating routine isn’t appropriate for everyone. It requires serious forethought and consultation with medical professionals to make sure it’s a good fit for your body and lifestyle.

Is the OMAD diet right for you? 

Deciding whether or not an OMAD eating schedule is right for you requires careful consideration of your goals, needs, body, lifestyle, and preferences.  

If you’re not sure if the potential benefits of OMAD are worth it — or if eating one meal a day benefits you at all — let’s run through some comparisons to help guide your thought process. 

The OMAD diet vs. time-restricted eating (TRE) schedules

Keeping in mind that we don’t recommend any form of fasting that lasts 18+ hours without approval from your healthcare provider, a TRE schedule in the form of 16:8 intermittent fasting, 14:10 intermittent fasting, or 12-hour intermittent fasting is more manageable and less risky without compromising on potential results — really a win all around! These intermittent fasting schedules are our most popular ones for a reason.

The Warrior Diet is also a form of TRE (20 hours of fasting and a 4-hour eating window), but again, unless you have medical support, going 18+ hours without food isn’t recommended. 

The OMAD diet vs. the 5:2 diet and alternate-day fasting

The 5:2 diet involves fewer days of fasting (you eat as you normally would for five days of the week) but two days of serious calorie counting and restriction (you eat only 500–600 calories). Alternate-day fasting is effectively the same concept, but you eat 500–600 calories every other day (so 3–4 days every week are fasting days). 

Since both of these schedules also involve 18+ hours of significant calorie restriction, we don’t recommend them as OMAD alternatives unless your healthcare team is on board. 

The OMAD diet vs. Eat Stop Eat

With an Eat Stop Eat schedule, you have five days of “normal” eating (whatever “normal” means to you), which may sound more appealing than fasting daily with OMAD … until you realize that the other two days involve going 24 hours without any food. As a highly restrictive form of fasting, it’s another one you really need to discuss with your doctor before attempting.

Written by Aly Owen

Medically reviewed by Josie Porter, RD