The one-meal-a-day (OMAD) fasting diet is a time-restricted eating pattern where you consume a single meal each day within an hour and fast for the remaining 23 hours. Many people may choose this more extreme fasting method to achieve weight loss, as well as those who have already tried other fasting methods.
Like all fasting methods, the number one rule of OMAD involves meal timing; however, what you eat still matters for the best results.
Let’s unpack all you need to know about the OMAD diet, including how it works, what the research says, and who it may (or may not) be right for. Because OMAD is one of the most restrictive fasting methods, we don’t recommend it for beginners or for most fasters.
However, if you decide to test-drive OMAD, we’ll walk you through how to do it in the safest way possible to support your goals without compromising your health.
Key Takeaways/TLDR:
- One meal a day (OMAD) is a restrictive fasting plan where you eat just one meal a day and fast the remaining 23 hours.
- Research on the benefits of OMAD compared to other fasting methods is mixed, with more potential health concerns due to its restrictive nature.
- OMAD is only appropriate for experienced fasters—and requires careful planning.
Always speak to your doctor or a registered dietitian before starting a fasting plan, especially if you take medications or have a chronic medical condition like diabetes.
What Is OMAD?
The one-meal-a-day (OMAD) diet is a form of intermittent fasting that involves eating one meal over a one-hour period and restricting calories completely for the remaining 23 hours.
The 4 rules of OMAD are:
- Fast for 23 hours
- Eat within a one-hour window
- Choose a nutrient-dense meal
- Stay hydrated
The traditional, strictest version of OMAD involves only one meal during this window, with no calorie-containing foods or beverages outside of this one hour a day. However, some follow more flexible variations where small amounts of low-calorie, nutrient-rich foods like lean chicken, fish, eggs, fruits, or veggies can be consumed during fasting hours to control hunger and maintain energy.
Most people who follow OMAD choose to have their one meal at dinner, but some may choose breakfast or lunch. For more flexible plans, a snack or a small, low-calorie meal outside this time may be enjoyed, but a calorie restriction is still recommended for the full benefits.
The potential benefits of this fasting method are thought to be related to fasting benefits in general and the associated calorie restriction from the very narrow eating window, even if small amounts of food may be eaten outside of it.
Potential Benefits of One Meal a Day
For more experienced fasters, the OMAD diet may offer similar health benefits to other fasting methods, such as 18:6, 14:10, and 16:8, which are less restrictive. Advocates of OMAD suggest that our bodies are programmed to fast for extended periods, as our ancestors did when food was scarce.
Weight loss
Because OMAD involves a very short eating window, it typically results in reduced calorie consumption. When you only have one hour to eat and little time outside of that, it’s more likely you will achieve a calorie deficit, which is required to lose weight.
One 2022 study showed that adults who restricted their eating window to even a 2-hour period in the evening (from 5:00 p.m. to 7:00 p.m.) experienced significantly greater body fat and weight loss than those eating separate meals throughout the day. Their calorie intake was equal, suggesting that there may have been a specific metabolic benefit to consuming one meal a day rather than three meals over a longer period.
However, this study was done in healthy, lean individuals and may not translate to the same results for different populations, such as those diagnosed with overweight or obesity. It’s also questionable how sustainable weight loss results would be on this diet, as its extreme nature can make it hard to stick to.
Improved insulin resistance
Research shows that fasting for at least 12 to 16 hours can improve insulin sensitivity in people with type 2 diabetes. While there are no research studies on one meal a day and insulin resistance specifically, it’s possible that it may provide these same benefits due to its prolonged fasting nature.
However, other studies show that following OMAD may worsen insulin resistance or increase the risk of hypoglycemia in some people, possibly due to a lack of food over a prolonged period of time. If you go a long time without eating and consuming glucose (e.g., carbohydrates), your blood sugar may decrease, and the body can become insulin-resistant as it tries to remember how to produce insulin once you’re eating again.
Heart health
Other fasting methods are linked to lower LDL cholesterol (the “bad” cholesterol), which can reduce heart disease risk. However, these studies have not specifically assessed these benefits with OMAD.
What we do know is that older studies show a link between OMAD eating and increased LDL cholesterol and blood pressure compared to less restrictive fasting regimens, which may be a concern even for those with optimal heart health.
Reduced inflammation
Some studies show time-restricted fasting schedules, such as alternate day fasting, have the potential to reduce inflammatory markers like C-reactive protein (CRP) if a significant weight loss is also achieved. However, more research is needed to determine if the OMAD diet provides these same anti-inflammatory benefits.
Downsides of OMAD Fasting
While there are certainly many benefits of fasting seen in the research, the consensus is less clear for more extreme methods like OMAD. In fact, the research identifies several potential risks worth considering, which is why it’s not a fasting method I often recommend to clients.
Increased hunger and risk for overeating
While OMAD can reduce calorie intake by shortening your eating window, it may leave you feeling hungry and increase the risk of overeating. You may find yourself ravenous once it’s time to eat, especially if you’re not used to this type of schedule.
Research shows this can occur with more prolonged fasting schedules like OMAD, where the hunger hormone ghrelin increases over time. In these studies, many find themselves experiencing more intense, hedonic-level hunger that can be hard to control as a result of this hormonal surge.
Worsened insulin resistance and hypoglycemia
Studies show that one meal a day may actually worsen insulin resistance, even in those without diabetes. In addition, longer fasting methods may increase the risk of hypoglycemia (e.g., low blood sugar) in those with type 2 diabetes, even if diabetes medications are reduced. When you are going a long time without eating and your body isn’t used to it, you may find your blood sugar lower than usual.
What this means⸺those who take insulin or other glucose-lowering medications should take special caution to discuss their new eating schedule with their doctor before starting, and insulin resistance and levels should be monitored in everyone following this diet plan.
Increased heart disease risk factors
While other fasting methods are associated with healthier hearts, it appears the body may respond differently to OMAD.
For example, some older research suggests that eating one meal a day is associated with higher LDL cholesterol and blood pressure than more flexible fasting approaches like 14:10 and 16:8.
More recent data from a study following over 24,000 adults also address similar concerns, where those eating one meal per day had an increased likelihood of heart complications and poorer long-term health outcomes.
This study compared the eating schedules of three core groups:
- Those eating one meal per day, similar to OMAD fasting
- Groups eating two meals or less per day, who skipped either breakfast, lunch, or dinner
- Those eating three meals per day
Overall, those having just one meal a day or two meals in 4.5 hours or less had the highest all-cause mortality (risk of death) out of any other group. Among groups that skipped one meal per day, those who skipped breakfast had the worst cardiovascular outcomes.
There are several potential reasons for this increased risk, based on what was seen and investigated in this study.
Skipping breakfast is often associated with other unhealthy dietary and lifestyle habits. Passing on breakfast is also associated with obesity and the risk of overeating later as your body and appetite try to play catch-up. While everyone is different, this may help explain why an earlier eating window may help you feel your best and better control your daily calorie intake, such as 7:00 a.m. to 3:00 p.m., rather than a later one, such as 12:00 p.m. to 8:00 p.m.
Skipping too many meals, such as in OMA,D can result in consuming more calories at the remaining meals, which can burden the body in a short time. If this continues, it may lead to metabolic impairments such as insulin resistance.
While not all the reasons for this increased risk are fully understood, it’s possible that OMAD may place additional strain on the body through these mechanisms.
Other potential side effects
Due to its restrictive nature, other possible side effects of OMAD include:
- Headaches
- Fatigue
- Dizziness
- Nausea
- Diarrhea
- Nutrient deficiencies
If you experience any of these when starting any fasting method, consult with your doctor or registered dietitian for guidance. The Fasting App by Municorn allows you to easily track your habits so you can catch potential side effects early if they arise.
Special Considerations
While the OMAD approach may work for some, it’s not the best method for everyone. It is not recommended for beginner fasters or those who are:
- Pregnant, trying to conceive, or breastfeeding, as a very short eating window will make it difficult to meet elevated nutrition needs.
- Have a history of an eating disorder, as diet rules and extreme restriction can exacerbate disordered eating behaviors
- Are diagnosed with uncontrolled diabetes, as medications may need to be adjusted or completely stopped during fasting times
- Are prescribed medication that needs to be taken with food or spread out throughout the day
Remember to always speak to your doctor and registered dietitian before starting a fasting regimen, even if you don’t have any of these contraindications.
What Should I Eat With OMAD Fasting?
When you’re only eating one main meal a day, every single bite counts. Focus on building one balanced, nutrient-dense plate (plus a small snack if allowed) using these core food groups.
- Vegetables
Load up half your plate with colorful veggies (especially leafy greens, broccoli, peppers, squash) for fiber, vitamins, and fullness without a ton of calories. - Fruit
Add 1–2 servings of fruit—like berries, citrus, or apples—for antioxidants, fiber, and a carb boost to support energy. - Lean proteins
Make protein the anchor: poultry, fish, eggs, tofu, beans, or Greek yogurt to help maintain muscle, support metabolism, and keep you satisfied. - Whole grains or starchy veggies
Include a modest portion of quinoa, brown rice, farro, oats, potatoes, or sweet potatoes for slow, steady energy and gut-friendly fiber to fill you up. - Healthy fats
Finish with avocado, nuts, seeds, or olive oil to support heart health, hormone balance, and satisfaction.
Picture one meal that covers all your bases⸺ protein, fiber, healthy fats, and complex carbs so your body isn’t missing key nutrients while you’re fasting the rest of the day.
Sample OMAD Meal
If you’re wondering how to fit in all the food groups in one meal, here are a few OMAD meal ideas to consider, whether it’s breakfast, lunch, or dinner.
*Portions may vary based on your unique nutrition needs.
Breakfast: Sunshine Scramble
- 3–4 eggs scrambled with spinach, mushrooms, and tomatoes
- ½ avocado
- 1 cup roasted sweet potatoes
- ½ cup berries on the side
This meal provides a generous amount of protein, antioxidants, fiber, and healthy fats packed into one sitting.
Lunch: Mediterranean Power Plate
- Grilled salmon (or tofu)
- Large Greek salad: mixed greens, cucumbers, tomatoes, olives, chickpeas
- ½–1 cup quinoa or farro
- Olive oil + lemon dressing
- Optional: Greek yogurt with berries for added calcium & probiotics
This meal is high in omega-3 fats, fiber, and minerals, making it a well-rounded meal.
Dinner: Protein-Packed Burrito Bowl
- Grilled salmon (or tofu)
- Large Greek salad: mixed greens, cucumbers, tomatoes, olives, chickpeas
- ½–1 cup quinoa or farro
- Olive oil + lemon dressing
- Optional: Greek yogurt with berries for added calcium & probiotics
This meal provides balanced macros, lots of volume to fill you up, and a simple, stress-free way to pack in veggies, complex carbs, and satisfying protein.
Expert Tips for OMAD Fasting Success
More experienced fasters or highly disciplined individuals may be curious about OMAD. While it is not the first-line approach we’d recommend here at the Fasting App, here are a few tips on doing it more safely if you decide to try it.
Start gradually
Do not attempt OMAD as a novice faster. If you have been fasting for several months and have been having success with more strict plans like 16:8 or 18:6, where you fast for 16 and 18 hours, you can slowly transition to a 23-hour fasting window to match an OMAD plan.
It may be best to do this over a few weeks, gradually narrowing your eating window from two meals to one, for example, to allow your body to adjust as much as possible.
Consider a more flexible approach
If the thought of eating only one meal a day sounds out of reach, consider a more flexible approach that lets you have mini meals or snacks throughout the day, such as small portions of lean chicken, fish, eggs, fruits, or veggies. The main goal is not to exceed your calorie needs to get the full benefits.
Be open to supplements
Since it can be difficult to get all of your nutrients in just one meal a day, supplements should be considered. This may be a multivitamin and mineral, fiber, or other single-nutrient supplements that you may be lacking in your diet. If you’re unsure what you need, get your blood levels checked and consult with your doctor and dietitian for individual guidance.
Get support/guidance
Fasting apps like the Municorn Fasting App can help you transition to your chosen eating window, send gentle reminders, and provide community support from others following the same plan as you. Tracking your meal intake and how you feel can also provide helpful insight into whether OMAD is working for you (or not).
Other Less Restrictive Fasting Methods
If OMAD is not for you, there are plenty of other less restrictive fasting methods you can consider, ranging from the most restrictive to the least restrictive.
- 18:6 method: Fasting for 18 hours and eating within a 6-hour window
- 16:8 method: Fasting for 16 hours and eating within an 8-hour window
- Alternate day fasting: Fasting every other day and eating as usual on other days
- 5-2 method: Eating as usual for five days and fasting or having limited intake on the other two days
- 14:10 method: Fasting for 14 hours and eating within a 10-hour window
- 12:12 method: Fasting for 12 hours and eating within a 12-hour window
These methods can offer the benefits of fasting and feel more sustainable.
Key Takeaways
The one meal a day diet (OMAD) is one of the most extreme forms of intermittent fasting, where all daily calories are consumed in one meal, and you are fasting the remaining 23 hours. While it can lead to potential benefits such as weight loss or improved insulin sensitivity, research also shows several important drawbacks to consider.
OMAD is not recommended for beginners or anyone with certain health conditions, and even experienced fasters should approach it with caution. If you do want to try the OMAD diet, speak to your healthcare provider or dietitian experienced with intermittent fasting to ensure you do it safely.
FAQs
- Is it healthy to eat one meal a day? Eating one meal a day may work temporarily for some, but it is generally not recommended by health experts. This is because it can be difficult to get all of your nutrients from that one meal alone. If you try it, it’s important to consider supplements to fill in any gaps in your diet.
- What is the best time for OMAD? There is no single best time for OMAD; the best time to have your one meal will depend on your preferences and schedule.
- Is OMAD better than intermittent fasting? OMAD is not shown to be superior to other less restrictive fasting methods, and it may actually pose more risks to blood sugar, cardiovascular health, and pose the risk of overeating.
- What happens if I eat one meal a day for 30 days? Following the OMAD plan for this long may lead to negative side effects like nutrient deficiencies, increased appetite, heart health risks like high cholesterol and blood pressure, and blood sugar complications. While it may cause initial weight loss, it’s unlikely to be sustainable.
