Is the OMAD Diet Plan Healthy (One Meal a Day)?

The human body is designed to function optimally when it receives a regular supply of nutrients and energy from food. In this article, we’ll review why it is not healthy for most people to eat only one meal a day. Learn about the OMAD diet plan and who should avoid it.

Why eat one meal a day?

Definition of the OMAD diet

OMAD stands for “one meal a day”. It isn’t technically a “diet”, as there is no particular eating plan involved. Nor are there any foods that you “should” or “shouldn’t” eat.

Instead, it is an extreme type of intermittent fasting, where you have a one-hour eating window for eating each day. For the remaining 23 hours of the day, you don’t consume any calories at all. 

There is no rule about the time at which this one large meal must be taken. Some people make it their first meal of the day, while others opt to save their hour for lunch or dinner. 

You are, however, allowed beverages to keep you hydrated, but these are limited to water, black tea, or black coffee. Low-calorie or diet drinks are not permitted.

Brief overview of the diet and its popularity

The main emphasis of OMAD is on calorie restriction. While you are allowed to eat any foods you like as part of your one meal – even foods that are not typically “healthy” –  the narrow time frame makes it hard to consume too much. This then creates a calorie deficit.

A further benefit of only eating once per day, say enthusiasts, is that it manipulates the ways in which your body uses the foods you eat. 

Ordinarily, your body will break down the carbohydrates you consume into sugars. Once the levels of sugar in your blood are sufficient, the hormone insulin – created by your pancreas – will carry the remainder to your fat cells.

If you go for a long period of time without eating, however, you produce less insulin. In order for your body’s cells to get energy for fuel, your fat cells release energy instead. This is also the rational for the keto diet.

For these reasons, the OMAD diet is gradually increasing in popularity as a tool for weight loss. 

The idea of fasting in order to lose weight is by no means a new one, but other approaches are a little less restrictive. 

The 16/8 method, for example, limits your eating to 8 hours per day and requires you to fast for the remaining 16. 

You may also have come across the Warrior Diet, which involves feasting for 4 hours and fasting for 20. These “diets” are more manageable than OMAD for many people.

Another form of intermittent fasting is the Fast 5 where you eat your daily calories within a 5-hour window. Alternate-day fasting is yet another one of the intermittent fasting diets.

Nevertheless, OMAD has its fans, who say it not only helps with weight loss but may also protect against heart disease, high blood pressure, erratic blood sugar levels, insulin resistance, and inflammation. The majority of the research supporting these potential health benefits, however, is focused on fasting in general rather than on OMAD specifically. 

And a recent review concluded that the lack of substantial research into fasting means we are not yet at the point where it can be recommended as a health intervention.

The potential risks and drawbacks of the OMAD diet 

OMAD may work for some people and it stands to reason that drastically cutting back on your food intake will initially lead to weight loss. 

But such a harsh regime is difficult to adhere to, so OMAD is not a sustainable long-term approach to eating. What’s more, skipping meals or drastically reducing the amount of food you eat can have negative effects on your health.

Potential problems include:

1. Nutrient deficiencies

In order to function effectively, our bodies need a broad spectrum of nutrients and sufficient calories.

It’s very hard to meet those requirements for nutritious foods with just one meal a day!

It would need to be calorie-rich and nutrient-dense, a tall order at the best of times but even harder to achieve when you’re exceptionally hungry and possibly craving unhealthy but satisfying foods.

There is a very real risk that OMAD can give you the urge to eat as much food as possible in your one-hour window. This is a compulsion that can lead to poor choices in terms of nutrition, leaving your body short of the vitamins and minerals it needs. 

Conversely, you might struggle to consume enough calories within a short period of time. Studies have shown that very low-calorie intakes can contribute to nutritional deficiencies and electrolyte abnormalities.

At the very least, an OMAD diet or OMAD meal plan should only be followed under the advice of a medical professional and ideally include input from a registered dietitian to ensure your nutritional needs are met.

2. Hunger and cravings 

Unsurprisingly, limiting your food intake to just one meal a day can lead to intense hunger. Studies have demonstrated that – compared to a more traditional eating pattern of 3 meals per day – fasting can increase the levels of ghrelin in your body. 

Ghrelin stimulates the appetite – and when you’re already dealing with the hunger associated with waiting 23 hours for a meal, that’s the last thing you need!

This is also problematic beyond being simply uncomfortable.

Firstly, this type of hunger on a daily basis can make OMAD a very difficult diet to stick to. That means any initial weight gains are quickly lost when you revert to previous eating habits.

Also, significant hunger can trigger cravings for calorie-dense foods like pizza and donuts. These are highly processed and offer little in the way of nutritional value.

Finally, there’s the emotional aspect to consider.

Being hungry can make you feel extremely irritable, potentially damaging your interactions with others and leading to a cycle of comfort eating in order to combat negative emotions.

3. Disrupting normal eating patterns 

A healthy relationship with food is important for long-term weight control and overall good health. A natural eating pattern – where we acknowledge that nutritious food is fuel for our bodies – forms part of this healthy relationship.

Severely limiting your food intake to just one hour or a single meal a day can significantly disrupt the natural pattern that your body is used to and damage this healthy attitude towards eating. 

In order to keep your biological timing system – or circadian clock – in sync, experts believe that we shouldn’t go for more than 12 hours without eating.   

4. Weight gain 

As mentioned earlier, it’s common to lose weight when initially embarking on the OMAD diet. This is because most people consume fewer calories than they normally would, creating an energy deficit.

But studies have shown that intermittent fasting (though not specifically OMAD) is probably no more useful in losing weight than simply consuming fewer calories at each meal when following a traditional eating schedule. 

See my related article on the dangers of intermittent fasting for women.

Cutting calories or caloric restriction – but eating at regular times throughout the day – is far more sustainable for most people than following the OMAD diet. 

Crucially, eating just one meal a day and fewer calories than you need may even cause you to GAIN weight. This is because your metabolism may slow down in order to preserve your energy levels. As your metabolism slows, the harder it becomes to lose weight. 

A 2008 study published in the British Journal of Nutrition suggested that eating on a regular basis may help you to burn more fat. 

What’s more, researchers found that the overall feeling of satiety from eating 3 meals compared to 2 – even though the total number of calories consumed was the same – was increased over a 24-hour period. 

In other words, eating the same number of calories over 3 meals per day as opposed to 2 helps you feel full for longer. It also helps you maintain a healthy metabolism. While this doesn’t relate directly to OMAD, it’s an example of how our bodies may react negatively to eating less often.

5. Changes in the menstrual cycle (for women of childbearing age)

Experts have always known that the reproductive cycle is influenced by your weight, your calorie intake, and how often you exercise.

While there is no scientific evidence that eating one meal a day can affect menstruation, one study involving young rats found that intermittent fasting and calorie restriction may have a negative impact on the hypothalamic-pituitary-gonadal axis. This refers to the glands responsible for the production of reproductive hormones. 

There is a risk, then, that the OMAD diet can lead to missed periods and potentially impact fertility.

See my related articles on the best diet for fertility and some healthy weight loss tips for women.

Alternatives to the OMAD diet

Eating one meal per day, also known as intermittent fasting or the “one meal a day” (OMAD) diet, is not a healthy or sustainable way to eat for most people. Let’s explore some other options.

Healthy and sustainable ways to lose weight and improve health

There are many steps we can take in our daily lives to keep our weight under control and improve our overall health. And the good thing is that these techniques are all sustainable, meaning you’ll reap the benefits now and well into the future.

• Cut out or reduce added sugar. Found in sweet drinks and many processed foods, added sugars have been linked to weight gain, heart disease, inflammation, and other conditions. See my list of the best no-sugar foods.
  
• Limit your intake of refined carbohydrates, found in foods like white bread and pasta. These have been stripped of their important nutrients and are low in fiber, so they don’t keep you full for long. Opt instead for complex carbs, found in whole grains, vegetables, and beans. Get my full clean eating shopping list.
  
• Focus on clean eating, which means choosing foods that are primarily unrefined and unprocessed. Ensure your diet contains plenty of lean protein and healthy fats, which will keep you feeling full and prevent overeating. Learn more about how to get started with clean eating.

• Increase your daily exercise by finding activities you enjoy. Start with a daily walk and add in other activities like swimming, spinning, badminton, etc. Learn to view exercise as a way of caring for your body rather than a punishment for overeating.
  
• Eat mindfully, chewing slowly and concentrating on flavors and textures. Avoid eating in front of the TV – it’s easy to eat too much without realizing you’re doing so!
  
• Plan your meals in advance and cook from scratch more often. It’s tempting to reach for processed meals and snacks on busy days, whereas a little forward planning can ensure you have healthy meals readily available. See my meal prep tips for beginners.
  
• Drink enough water. Thirst is often mistaken for hunger, so staying well hydrated can prevent you from eating unnecessarily.
  
• Maintain a support network. If you don’t have friends or family who are interested in helping you achieve your goals, use social media to find groups for mutual support and encouragement.

The importance of a balanced diet and regular, nourishing meals

A healthy, balanced diet is rich in whole foods like fruits, vegetables, legumes, seeds, nuts, whole grains, fatty fish, and lean proteins. A wide range of clinical studies has shown us that a healthy diet plays an enormous part in reducing the risk of noncommunicable diseases (NCDs) like heart disease and cancer.

What’s more, experts agree that eating 2 or 3 meals a day is better for you than limiting your calorie intake to one meal. 

Consuming nourishing foods at regular times gives you the energy you need to accomplish daily tasks. It also keeps your sugar levels steady, improving your mood and sense of well-being.

FAQs About OMAD Diet

Conclusions

There may be situations where the OMAD diet can be useful, and for some people, it may be helpful in achieving short-term weight loss. 

However, the general consensus is that – for most people – it is unsuitable in the long term, being both hard to sustain and associated with a number of risks.

Our bodies function best when we supply them regularly with the nutrients obtained from a whole, healthy, and balanced diet.

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Note: this post is for informational purposes only and is not intended as medical advice. Please consult your healthcare provider for recommendations related to your individual situation.

About the Author: Carrie Forrest has a master’s degree in public health with a specialty in nutrition. She is a top wellness and food blogger with nearly 10 million annual visitors to her site. Carrie has an incredible story of recovery from chronic illness and is passionate about helping other women transform their health. Send Carrie a message through her contact form.