OMAD Diet: Is It Healthy to Eat Once a Day?

The other day, I was at the gym and heard two gymgoers discussing a new diet one was looking to try. As a registered dietitian, this intrigued me. I soon found they were talking about the OMAD diet, which I was not familiar with, that is, until I did some digging.

While I learned that celebrities like Bruce Springsteen and Chris Martin reportedly follow this diet to supposedly help ‘burn fat,’ it has also been further popularized on TikTok. Is this true? Are celebrities and influencers onto something?

In this article, I’ll explain what the diet is, break down the research, and share my perceptions and advice as a registered dietitian.

What is the OMAD diet?

The OMAD diet stands for ‘one meal a day’ and is a variation of intermittent fasting that involves reduced meal frequency and long daily fasting periods. Proponents of this eating pattern believe it may help with weight loss efforts.

Intermittent fasting is a time-restricted pattern of eating. Thus, it is less about the types of foods you consume and more about when you consume them versus when you fast.

While there are different interpretations of the OMAD diet, the general consensus is that it is designed to restrict your eating window to one hour per day. While there are no specific food restrictions, those following it typically only drink water during fasting periods.

Further, typically, proponents encourage eating a nutrient-dense meal, one that makes up most of but not more than your daily calorie needs for the day.

How does the OMAD diet work?

In theory, this eating pattern is not geared at extreme energy restriction for weight loss, but rather the potential to support more efficient blood glucose regulation and thus reduce the likelihood of fat gain.

Since the idea of this eating style is less about extreme calorie restriction, the theory is that weight loss may occur due to decreased spikes in blood sugar from not eating for extended periods of time.

Typically, when you consume food (particularly carbohydrates), blood sugar levels rise, and your body uses these sugars for energy. Any leftovers may be stored as fat.

However, not all carbohydrates are equal, as those containing fiber or those eaten with other foods containing protein and fat may help to anchor blood glucose levels and thus prevent sudden and high blood sugar spikes.

While the theory could be plausible, in practice, it may be quite difficult to meet your daily calorie needs with only one meal, which could lead to a caloric deficit that may actually contribute to proposed weight loss.

Moreover, weight loss, as the primary proposed benefit of this eating pattern, is not so simple to be determined solely by blood glucose management, as weight loss requires multifactorial food and lifestyle interventions to reach the goals.

Is it healthy to eat once a day?

Currently, there is no reputable medical or nutrition body that recommends only eating once per day.

While some people may choose to eat just once per day for personal or cultural reasons, from a health perspective, this is not recommended, and if you choose to do so, you should be monitored by a doctor for safety reasons.

Potential health benefits of the OMAD diet

While weight loss may occur on the OMAD diet, the potential benefits do not outweigh the potential downsides. Further, there are no reputable bodies that recommend this eating pattern for weight loss or to support overall health.

Regarding weight loss, one small study examined the effects of consuming three meals per day versus one meal a day in 13 healthy adults. Calorie intake across the groups was similar, but the one-meal-a-day group consumed an average of 110 calories less per day.

While the study findings concluded that consuming one meal a day in normal-weight individuals decreased body weight compared to the three-meal-per-day group, the length of the study was short, and the sample size was quite small, so further larger and long-term studies are needed.

Further, a meta-analysis indicated that an intermittent fasting, energy-restricted diet in high body mass index (BMI) individuals resulted in weight loss. However, these effects were not superior to a continuous caloric-restricted diet, which equally reported considerable weight loss.

Moreover, the subjects used for these studies were mainly overweight or obese, and different intermittent fasting eating patterns were used, so these results aren’t comparable or generalizable to the average population.

In my opinion, fasting for prolonged periods may lead to uncontrollable cravings and/or extreme hunger during fasting hours, and if you only eat one meal a day, these symptoms may occur.

Keeping all of this in mind, I also reached out to Sandra Vigelienė, health content researcher and nutritionist, for her input:

Sandra Vigelienė, BSc

Health Content Researcher

While the OMAD diet may induce a caloric deficit potentially leading to weight loss, its long-term sustainability and maintenance of results remain key concerns, among other factors. Over time, the body may adapt to the reduced energy intake, potentially causing the initial rate of weight loss to plateau. This adaptive response could necessitate periodic adjustments to the dietary pattern, which may contribute to fluctuations in body weight and the potential for a yo-yo dieting effect, where maintaining the desired weight becomes difficult, among many other concerns this particular eating style bears.

Overall, even though the OMAD diet may help some lose weight, it’s not advisable to follow this eating pattern as it is unlikely to be sustainable and has potential safety concerns.

Is the OMAD diet safe?

No, based on the best available evidence and my experience as a dietitian, the OMAD diet is not entirely safe, especially long-term. This type of intermittent fasting may lead to prolonged periods of hunger, which may lead to dizziness and/or low energy.

Further, potential safety concerns of this type of intermittent fasting include:

• Increased risk of low blood sugar, which may lead to fainting and or decreases in physical performance during exercise
• Nutrient deficiencies (particularly if followed long-term)
• Muscle loss, as it can be difficult to meet protein needs
• Constipation may occur as fiber intake is likely decreased, and it would be challenging to meet your daily fiber needs when you only eat one meal a day

Further, particular groups may have different nutritional needs from the average population, and they are at higher risk and should not follow an OMAD diet. These groups are:

Getting all your nutritional needs met in just one sitting: is it possible?

While it is theoretically possible to consume all of your essential nutrients in one sitting, practically speaking, it is unlikely you can get enough nutrients to meet your needs.

For example, one client I counseled in the past was focused on muscle building and trying to consume large amounts of protein at a single meal, sometimes up to 60–80 grams per meal.

However, although the body can theoretically absorb limitless amounts of protein, it can only effectively utilize around 20–25 grams per meal for young adults, with no benefit at more than 40 grams per single meal, depending on age and amount/type of exercise.

Thus, although my client was more than meeting his protein needs for the day, he was essentially ‘wasting’ extra protein that his body was either using for energy or converting and storing as fat.

This is just one instance of many regarding nutrient absorption and utilization, which is why I do not recommend consuming all of your essential nutrients in just one meal a day.

Further, even though I don’t personally follow the OMAD diet, as a dietitian, I do try to consume well balanced meals most of the time. Even so, I know from personal experience that it still can be a challenge meeting all of your nutrient needs in a day, never mind one meal.

This is why I recommend consuming a well-balanced meal three times daily and focusing on how you can meet your nutrient needs throughout the day as opposed to just one meal.

Less extreme ways to manage weight and health

If you choose to attempt to lose weight, I highly recommend working with a health professional team, as weight loss is complex and can be dangerous if the necessary precautions aren’t followed.

One meta-analysis highlights that calorie restrictions of 500–700 calories per day have been used to help support obese patients with weight loss. However, in practice, as a dietitian, I would advise a more moderate reduction (if appropriate) as this calorie deficit likely isn’t sustainable.

From working with diverse patients, I know that dietary needs are individualized and based on various factors like health status, lifestyle, personal beliefs, and more. This is why personalized nutrition plans are important. Generalized diets or eating patterns are often not appropriate or ineffective long-term.

While studies on less extreme versions of intermittent fasting (eating windows of ~8–10 hours) are promising, a large body of evidence suggests that restrictive weight loss diets may not work long-term. In fact, one study found that only roughly 27% of participants were able to keep more than 10% of their initial body weight.

While I don’t currently counsel individuals on how to lose weight, the research appears to align with results from friends and family who share their weight loss journey with me.

Instead of focusing on any one particular diet, I advise individuals to follow the American Dietary Guidelines and use these simple tips to help create sustainable lifestyle changes that may help support their overall health:

• Eat more plant foods and complex carbs. Plant foods and whole grains are often high in fiber, which is important for maintaining blood sugar levels and a healthy weight, cholesterol levels, and promoting bowel regularity. Aim to make half of your plate fruits or vegetables.
• Eat lean proteins most often. Swap meat for lean or extra lean cuts and choose plant-based protein sources like tofu, lentils, and beans whenever possible.
• Consume more healthy fats. Fats from foods like avocados, olives, nuts, seeds, and fatty fish are good for heart health.

Bottom line

The OMAD diet is an extreme version of an intermittent fasting diet, advertised as a weight loss diet. Time-restricted eating can be dangerous, particularly for certain vulnerable groups.

The reality is that weight control can be challenging and, in some cases, not appropriate. However, if you are seeking weight loss, work closely with a healthcare professional who will help you with a sustainable approach and ensure your nutritional needs are met.