OMAD Diet: Is it Safe and Effective?

In recent years, intermittent fasting has gained significant attention, and the OMAD diet is one of its popular variations. Abbreviated for “One Meal A Day,” the OMAD diet involves consuming all your daily calories in a single meal. But how effective is this approach, and more importantly, is it safe?

In this article, we’ll explore the benefits and drawbacks of the OMAD diet, its potential for weight loss and provide expert insights from nutrition expert Melissa Mitri, MS RD.

What Is the OMAD Diet?

The OMAD diet can be seen as a more extreme version of intermittent fasting. While most intermittent fasting methods involve a more even rotation of alternating eating windows and fasting windows, the OMAD approach is much more stringent: it requires fasting for 23 hours and eating just one meal within a one-hour window each day. For the best results, it’s recommended to keep this one-hour eating window consistent each day.

Although the OMAD diet doesn’t restrict what you can eat during your eating window, sticking to a balanced, nutritious meal is key to maximizing the benefits, particularly if you’re looking for the benefits of a weight loss diet. During the fasting period, you are allowed to consume zero-calorie beverages, such as water or black coffee, which can help keep you hydrated without breaking the fast.

Is the OMAD Diet Safe?

It’s important to note a few risks associated with the OMAD diet. Since you are only eating within a one-hour timeframe, there is a risk of nutrition deficiencies. This diet is also associated with hypoglycemia or low blood sugar since the body goes a long time without carbohydrates to keep blood sugars at a healthy range. This level of restriction can also lead to unpleasant symptoms like nausea, dizziness, fatigue, extreme hunger, irritability, and constipation.

Melissa Mitri, MS RD

Weight Loss Expert, Nutrition Writer and Media Dietitian

You may also like:

Can You Drink Coffee While Fasting?

Turmeric Lemonade For Weight Loss: Overview, Benefits & Recipe

What Can You Eat in the OMAD Diet?

The OMAD diet lets you eat whatever you want, but that doesn’t mean you should. At least not if you wish to make the most of it! Since you’re only eating once a day, it is good to ensure you have adequate calorie intake, along with the necessary nutrition.

If you were to consume high-calorie or unhealthy fatty foods during your short eating window, you are still likely to gain weight rather than lose any. The Mediterranean diet is one of the best to combine with intermittent fasting [1] for the variety of benefits it offers. The food groups that fall under this diet include:

• Leafy vegetables and fruits, beans
• Plant-based protein like lentils
• Fish and other seafood
• Healthy fats like avocados and extra virgin olive oil
• Whole grain foods like brown rice, whole grain bread, quinoa
• Moderate amount of eggs, yogurt, natural cheese, and poultry meat

What is the best time to eat while on the OMAD diet?

For weight loss purposes, some research suggests eating in the morning may be preferred. However, this is not always the case, and it comes down to a matter of personal preference. [2] If you workout in the morning, for example, you may prefer to have a late breakfast or lunch as your one meal to refuel. If you are a night owl or want to eat dinner with your family, you may prefer to have your meal in the evening.

Melissa Mitri, MS RD

Weight Loss Expert, Nutrition Writer and Media Dietitian

Is The OMAD Diet Effective for Weight Loss?

There is a lack of any specific research regarding the OMAD diet’s effectiveness for weight loss. However, evidence for intermittent fasting can help us understand how it can work. A review article published in the journal Nutrients reveals how intermittent fasting has positively affected weight loss, metabolic health, and insulin resistance. However, it isn’t shown to be much more significant than a calorie-restricted diet.

But, time-restricted eating has been proven to have weight loss effects. This is proven by a 2020 review in The Journal of Physiology, which discovered that time-restricted eating can help reduce body weight by 1-4%.

Is OMAD a good way to lose weight?

The OMAD diet is not the ideal diet to lose weight, as it’s too restrictive and can lead to intense hunger and eating disorder tendencies. This can increase the risk of overeating or bingeing, making it difficult to stay within a calorie deficit to lose weight. In short, OMAD is not a sustainable weight loss plan.

Melissa Mitri, MS RD

Weight Loss Expert, Nutrition Writer and Media Dietitian

Benefits of the OMAD Diet

While still under research, the OMAD (One Meal A Day) diet may offer a range of potential health benefits based on the broader science of intermittent fasting. While more research is needed to conclusively determine its effectiveness, there are some potential benefits associated with this eating pattern.

1. Potential for Fat Loss

A 2021 study published in Frontiers in Physiology explored the effects of eating one meal per day on metabolism and physical performance. The study found that participants who ate only one meal a day experienced a reduction in body weight, although the decrease was not substantial enough to show significant weight loss. The participants also maintained their physical performance levels, suggesting that OMAD may help with fat loss without negatively affecting exercise capacity. However, due to the small sample size (only 13 participants) and short duration (11 days), more research is needed for clearer conclusions.

2. Improved Metabolic Health

Intermittent fasting has demonstrated benefits for improving metabolic markers such as blood sugar levels. A study on time-restricted eating (not specifically OMAD) found that a 6-hour eating window followed by an 18-hour fasting period helped improve blood sugar control in adult men with prediabetes and obesity [3]. It also effectively improves insulin sensitivity and helps in managing blood pressure.

3. Enhanced Mental Alertness

Fasting can increase the release of orexin-A, a neuropeptide that helps regulate wakefulness and alertness. While this effect isn’t exclusive to OMAD, many individuals report feeling more mentally alert and focused during the fasting window [4]. For those who practice OMAD, fasting during the daytime can provide an energy boost, though this effect would likely be less pronounced if the single meal is consumed as a morning breakfast rather than waiting until later in the day.

4. Potential for Increased Weight Loss with Morning Eating

While the OMAD diet doesn’t specify which meal to eat, A 2019 study published in Nutrients suggests that those who eat a larger meal in the morning and fast overnight may experience more significant weight loss than those who eat in the evening. Fasting overnight and consuming a hearty meal in the morning can help regulate hunger hormones and improve energy utilization, which might support more effective weight loss over time.

You may also like: How Many Calories Should I Burn a Day?

Drawbacks of the OMAD Diet

The OMAD (One Meal A Day) diet has several drawbacks that make it difficult to sustain and may not be as effective as it seems:

1. Hard to Maintain

OMAD is a strict and extreme diet. Its restrictive nature can lead to feelings of deprivation, fatigue, and social isolation, making it difficult to stick with long-term.

2. Increased Hunger and Cravings

Fasting for 23 hours increases hunger by raising ghrelin levels, which may lead to overeating during the one-hour meal window [5]. This can cause weight gain rather than loss, and symptoms like dizziness, fatigue, headaches, and low blood sugar can also occur.

3. Nutrient Deficiencies

Eating just one meal a day makes it hard to meet all your nutritional needs, risking deficiencies that can lead to fatigue, weakened immunity, and bone health issues. It can also lead to eating disorders.

4. No Greater Effectiveness Than Calorie Reduction

While OMAD restricts calories by default, it’s unlikely to lead to more weight loss than simply reducing calorie intake throughout the day. Extended fasting may also cause overeating when it’s time to eat, undoing any benefits.

5. Potential for Unhealthy Eating Habits

OMAD allows all foods during the eating window, but extreme hunger may lead to unhealthy choices, such as overeating high-fat, calorie-dense foods, which could counteract weight loss goals.

6. Unsustainable Long-Term

Extreme diets like OMAD can foster an unhealthy relationship with food and may not be sustainable, especially in social situations or while traveling. Deprivation can also lead to eventual weight regain.

Do you gain weight back after OMAD? 

Most people will regain their weight after OMAD. This is because its rules are too restrictive, which increases the risk of overeating and makes it difficult to sustain. A more flexible fasting routine, such as a 16:8 schedule, maybe more feasible long-term.[6]

Melissa Mitri, MS RD

Weight Loss Expert, Nutrition Writer and Media Dietitian

You can also check out:

A Guide on How To Lose 5 Pounds in a Week

How Long Can You Go Without Food?

Conclusion

While OMAD might offer quick weight loss, it’s difficult to maintain, may lead to nutrient deficiencies, and could ultimately result in unhealthy eating patterns. It’s not a long-term solution for most people and is not commonly recommended by medical professionals. However, if you are still motivated to reap its benefits, please consult your physician before taking on any diet strategy. For guidance and tips on an effective weight-loss method, check out the JustFit app!