OMAD Diet: Eat One Meal A Day In This Form Of Intermittent Fasting

Certified holistic nutrition consultant By Lindsay Boyers
Certified holistic nutrition consultant
Lindsay Boyers is a nutrition consultant specializing in elimination diets, gut health, and food sensitivities. Lindsay earned a degree in food & nutrition from Framingham State University, and she holds a Certificate in Holistic Nutrition Consulting from the American College of Healthcare Sciences.
Medical review by Wendie Trubow, M.D., MBA
Functional Medicine Gynecologist
Wendie Trubow is a functional medicine gynecologist with almost 10 years of training in the field. She received her M.D. from Tufts University.
OMAD Is A Trendy Type Of Intermittent Fasting—But Is It Effective?

OMAD, an acronym that stands for “one meal a day,” is an extreme form of intermittent fasting that’s gaining a lot of traction in the nutrition world. The OMAD diet involves eating one large meal within one hour and then fasting for the remaining 23.

While the OMAD diet naturally leads to calorie restriction, its benefits come more from autophagy, a cellular process that clears waste from the body and helps improve overall health and longevity. If you’re considering working OMAD into your life, understanding the benefits and the risks can help you make the decision that’s right for you.

What is the OMAD diet?

Although OMAD is considered an extreme form of intermittent fasting, it’s actually really simple: Eat one large meal each day, within a one-hour time frame, and then fast for the other 23 hours. Aside from that, the only other real rule with OMAD is to stick to the same daily schedule.

That means, if you decide you’re going to eat between 3 p.m. and 4 p.m. (one of the most common eating windows for people following OMAD), that will be your ongoing eating window.

But while the OMAD diet outlines when to eat, there aren’t a lot of specific rules about what to eat. There’s no strict breakdown of macronutrients or calorie guidelines to follow. As long as you’re sticking to your eating window, you’re technically following OMAD.

That being said, as with any dietary plan, it’s always a good idea to make healthy choices when you do eat. Amy Shah, M.D. says, “Avoid carb-loaded meals and sugary drinks as they will cause a blood sugar roller coaster, raising your insulin levels and making you feel even more hungry." 

Shah adds that refined carbohydrates aren’t just a problem in the moment, they also make fasting the next day even more difficult because hunger hormones, like ghrelin, will be raised and you’ll feel hungrier. During your hour eating window, try to stick to lean proteins, healthy fats, and plenty of vegetables. 

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Benefits of OMAD.

Because OMAD is a form of intermittent fasting, the theory is that it comes with many of the same benefits, just with a smaller eating window. These are some of the potential benefits of eating one meal a day:

1. It's simple to follow.

One of the biggest benefits of the OMAD diet is simplicity. Because you’re only eating once per day, and there aren’t any rules about what to eat, there isn't a lot of meal prep or forethought required. The only thing you have to really think about is when to break your fast and then stick to that same schedule on the days you incorporate OMAD.

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2. It may help manage weight.

While you can lose weight with any type of calorie restriction, one research review compared intermittent fasting to regular, daily calorie restriction to see the effects on body composition. They found that while types of calorie restriction can lead to weight loss, intermittent fasting may help promote a greater amount of fat loss, while also helping retain lean body mass (or lean muscle).

Another small study with 32 participants found that even when overall calories weren't restricted, eating all calories in one daily meal resulted in greater loss of body fat. However, it’s important to point out that researchers from that study also found that eating one meal a day led to slightly increased blood pressure and cholesterol levels (although it did decrease cortisol levels too).

3. It could improve metabolic health.

What’s even more impressive is that intermittent fasting might help improve various health markers, even without weight loss. In one small study, researchers had pre-diabetic men follow different intermittent fasting schedules, but gave them enough food to maintain their current body weight. After 5 weeks, the men had better insulin levels, improved insulin sensitivity, and better beta cell response. They also saw improvements in their blood pressure and had decreased oxidative stress levels.

Another small followed 10 obese men with type 2 diabetes who were currently taking metformin, one of the most popular diabetic medications. After two weeks of fasting, the men had better blood sugar control than when they first started the study.

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4. It may improve mood.

Intermittent fasting isn’t just about the physical benefits, there are also mental benefits too. One study showed that prolonged fasting can increase availability of serotonin—a mood-boosting neurotransmitter—in the brain. It may also boost natural opioid and endocannabinoid production.

5. It could increase longevity.

Although a large amount of the research on intermittent fasting and longevity has used animals as subjects, the results are promising. As one review points out, research indicates that reducing your food intake through fasting can significantly increase your lifespan.

In fact, one of the longest-running animal studies focused on prolonged fasting found that rats could increase their lifespan by as much as 80 percent. However, the effects of fasting also depends on sex, age, overall diet, and genetic factors. 

But while there’s definitive research on less intense types of intermittent fasting, there isn’t a lot of focused science on whether or not going for longer periods without eating (as with OMAD) has additional benefits. 

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Is there anyone who should not try an OMAD diet?

Just like with any form of intermittent fasting, there are some people who shouldn’t try OMAD at all. If you have Type 1 diabetes, OMAD may not provide enough nutrients to keep your blood sugar levels steady through the day, especially in the initial phase when your body is adjusting to it.

While an OMAD diet isn’t strictly off-limits for women, women are generally more sensitive to the hormonal effects of fasting due to a protein called kisspeptin. If you’re a woman and you’re considering OMAD, or any type of fasting, make sure you’re familiar with the potential concerns surrounding fasting and women before jumping right in.

If you’re currently under a great deal of stress and are having trouble handling day-to-day life, hold off adding additional stressors, like OMAD, until you get everything else under control. It’s also a good idea to stay away from restrictive eating plans like the OMAD diet if you have a history of disordered eating or you’re pregnant or breastfeeding. And keep in mind that it's meant for adults, not children or young adults.

Tips for starting an OMAD diet. 

If you don’t fall into any of the above categories, but you still want to try an OMAD diet, there are some simple tips and tricks that can help get you started.

Even though there are no strict rules about when to eat your meal on the OMAD diet, research shows that you may be better off getting all your calories in before the evening. According to one study, eating calories after 5 p.m. was associated with a significant increase in levels of C-reactive protein (or CRP), an inflammatory marker that’s been connected to breast cancer, heart disease, and other chronic conditions.

Instead of jumping right into OMAD, Taz Bhatia, M.D., a board-certified physician specializing in integrative medicine, says “you can always start slowly, with shorter and gentler fasts a couple times a week, and see how your body responds.” While you may feel great during these short fasts, she adds “You may discover that fasting doesn’t work for you at all, and that’s okay, too.” 

The goal is to find a plan that works for you by gradually increasing the duration and frequency of your fasting over the course of several weeks to a month to give your body time to adjust. If you’re new to intermittent fasting, start with an easier-to-follow plan, like the 16:8 method, and then work your way into OMAD.

Some other tips to get you started and increase your chances of success include:

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1. Make your meal count.

Since you’ll only be eating one meal a day, you need to make sure you’re getting as many nutrients as possible in that meal. Focus on lean proteins, healthy fats, and lots of different types of veggies. And don’t eat the same thing all the time. Varying your food choices helps optimize your overall nutrient intake.

2. Limit the overall amount of carbs in your diet.

This helps balance blood sugar levels and your hunger hormones, which can make it easier to stick to a fasting schedule.

3. Adjust your fasting schedule accordingly.

While the idea is to eat within an hour and fast for the other 23, your plan can look a little different than that. If it takes you 90 minutes or two hours to eat, and you fast for 22 hours, that’s okay too. The major goal is to stick to one nutritionally-balanced meal per day and eat around the same time daily.

How long should you follow OMAD?

The OMAD diet isn’t meant to be a long-term dietary solution. It’s more of a “refresher” that you can incorporate once or twice per week or whenever you feel like your body and your digestive system need a little break. 

There are no hard rules about how long you should follow OMAD, but it’s important to always listen to your body and check in with how you’re feeling to see if you need to make any adjustments to your routine.

The bottom line

The OMAD diet is an extreme form of intermittent fasting that requires you to abstain from eating for 23 hours and get all your calories in a one-hour feeding window. It appears to offer many of the same health benefits as other forms of intermittent fasting, like weight loss, improved mood, better metabolism, and balanced blood sugar levels.

However, it’s not for everyone. If you have Type 1 Diabetes, are under chronic stress, or are pregnant or breastfeeding, you should steer clear of OMAD (and any other type of intermittent fasting). If you do decide to try OMAD, ease in slowly over a period of several weeks and make sure you’re regularly checking in with your body and making adjustments based on how you feel.

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