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

OMAD, an acronym that stands for “one meal a day,” is an extreme form of intermittent fasting that’s garnered a lot of buzz 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.

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." 

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.

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 composition2.

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, controlled study with 32 participants found that even when overall calories weren't restricted, eating all calories in one daily meal3 resulted in greater loss of body fat.

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 schedules4, 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 study followed 10 obese men with type 2 diabetes who were currently taking metformin, one of the most popular diabetic medications.

Intermittent fasting isn’t just about the physical benefits, there are also mental benefits too.

Although a large amount of the research on intermittent fasting and longevity has used animals as subjects, the results are promising.

As one 2019 review points out, research on animals and humans indicates that reducing your food intake through fasting can significantly slow or reverse aging.

In fact, one of the longest-running animal studies focused on prolonged fasting7 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. 

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 kisspeptin8.

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. As always, consult with your doctor to determine the right plan for you.

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.

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 protein9 (or CRP), an inflammatory marker that’s been connected to breast cancer, heart disease, and other diseases.

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.

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.

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 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. 

The OMAD diet is a more intense 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).