OMAD - an abbreviation for One Meal A Day - is a popular pattern of eating many are using to lose weight or improve metabolic health. But is it a healthy and sustainable way to lose weight? And is it a healthy long-term lifestyle? This guide will answer these questions and help you understand if OMAD is right for you.
What is OMAD?
Simply put, OMAD means eating one meal in a day. It doesn't specify what you eat, or even what time you eat. It simply directs you to eat once.
OMAD is the longest form of time-restricted eating, equivalent to a 23:1 fast (fasting for 23 hours and eating in a 1-hour window). In its purest sense, OMAD doesn't dictate calorie restriction or specific macronutrient composition. That said, we encourage you to continue your healthy, low-carb diet at that meal. And be sure to keep reading to the end for other practical tips for eating OMAD.
Benefits of OMAD - clinical experience
Clinicians experienced in prescribing intermittent fasting and low-carb nutrition frequently use OMAD as a tool to help with weight loss stalls. When a patient is eating low carb but isn't losing weight as expected, temporary use of OMAD can help kick-start weight loss. You can read more about addressing weight loss stalls in our evidence-based guide.
Many who eat in an OMAD pattern do so for the ease of only preparing food and eating once each day. This can be especially helpful for those who travel frequently, those who perform shift work, and those with hectic and busy schedules.
Think about how much time you spend planning, shopping for, and preparing meals. (And we haven't even mentioned dealing with dirty dishes.) If you eat three meals per day, how much time could you save by cutting that by two-thirds?
As a form of time-restricted eating and intermittent fasting, OMAD may help reduce hyperinsulinemia, control diabetes and improve metabolic syndrome. Consistent clinical experience shows that widening the fasting window can help improve these metabolic conditions. So, when used appropriately, OMAD could potentially deliver better results than shorter fasts.
Some see OMAD as an "easy" way to reduce calorie intake. When you only allow yourself to eat in a 30-to-60-minute time window, it is physically difficult to exceed your daily calorie needs. It's not impossible (just ask hot dog speed-eating champion Joey Chestnut, who can eat more than 10,000 calories in 10 minutes) but it sure is challenging. For those who benefit from a firm schedule that restricts snacking, OMAD can be the strategy that works best. (Of course, "easy" is in the eye of the beholder!)
Concerns about OMAD
Eating disorders
Any eating pattern that promotes a cycle of food restriction followed by extra food consumption can trigger disordered eating behavior in susceptible people. So if you have a history of eating disorders, you should probably avoid OMAD.
Chronic caloric restriction
Creating an environment where you naturally reduce caloric intake is one of the clinical benefits of OMAD. The other side of that coin is that it can be difficult to obtain adequate calories if eating OMAD long term on a daily basis. OMAD can then start to look a lot like chronic caloric restriction. Although chronic caloric restriction helps with initial weight loss, it poses long-term concerns because it tends to lower resting metabolic rate, which makes weight loss very difficult to maintain.
Inadequate protein intake
Just as OMAD promotes caloric restriction, it can also lead to protein restriction. Since protein helps you feel full and satisfied, it can be difficult to eat your entire daily requirement in one sitting.The average 5'10," 81-kg male should eat about 110 grams of protein daily (read more about how much protein we should eat ). If you can eat a 16-oz ribeye plus a couple of fried eggs in one sitting, then it may not be a concern. But if that sounds like a lot to you, then your protein intake may be too low with daily OMAD.
Excessive carb intake
If you are trying to consistently remain in ketosis, we recommend restricting net carb intake to less than 20 grams per day. But in general, we also advise that you spread out your carb intake so each meal has no more than 10 grams. With OMAD, you eat only one meal, so you could theoretically eat all 20 grams of carbs in one sitting. While that is still compatible with a keto diet, those who are highly insulin resistant may respond to a 20-gram carb load with glucose and insulin spikes.
GI upset and diarrhea
Some find the consistent cycle of no food followed by a large amount of food causes abdominal discomfort and even diarrhea. Although it's hard to estimate how many OMAD eaters experience this, our clinical expert panel considers it uncommon but not unheard of.
Taking medications with food
For those who need to take prescription medications with food more than once per day, OMAD presents a significant hurdle. If this is the case for you, discuss with your healthcare provider if other options exist. If not, then OMAD is likely not safe for you.
Exercise
Some people find it difficult to exercise while fasting. If you are active, this would make following an OMAD pattern challenging. However, we encourage you to at least try fasted exercise, as some findings suggest that it may help with weight and fat loss (although the literature is inconclusive on this point).
Warning signs
Many people do well, even thrive, with time-restricted eating and intermittent fasting. Others are more susceptible to side effects. Feeling a little hungry and a little low in energy are expected. But feeling unwell, extremely fatigued, dizzy, nauseated, or having other severe side effects are abnormal responses to intermittent fasting and OMAD. If you experience any of these severe side effects, OMAD is likely not the best choice for you. You can work with your doctor to determine if any changes (like greater adaptation to low carb and shorter fasting regimens) could make it an option in the future.
What does the science say?
The science on intermittent fasting and time-restricted eating is growing, seemingly on a weekly basis. The problem is that different studies investigate different protocols. For instance, one recent study showed that a 14:10 time-restricted eating pattern can promote weight loss and metabolic health. How do we know if these benefits occur with OMAD? If 14:10 is helpful, is 23:1 better? It might be. If lowering insulin levels and mobilizing fat stores for 14 hours is beneficial, it makes sense that doing it for 23 hours could be even more so. Yet this assumes that a longer time frame doesn't introduce any counterbalancing, negative effects.
Other studies suggest longer fasting windows have a net benefit, although none capture OMAD eating perfectly. For instance, another trial showed that in obese patients with diabetes, two weeks of eating within a 7-hour window (17 hours of fasting) reduced fasting and postprandial blood glucose more than eating within a 13-hour eating window (11 hrs of fasting).
Closer to a standard OMAD, a 2009 crossover study compared eating 3 meals per day to eating the exact same food allotment in a 20:4 eating window. The diet was 15% protein, 35% fat and 50% carbs. During the 8-week period of eating within a 4-hour window, participants lost 4.4 pounds (2 kg) of body fat while maintaining their lean mass. By contrast, they lost no weight or fat while eating three meals per day. In addition, immediately after the time-restricted eating portion of the study, patients had lower triglycerides (93 vs 102 mg/dL), higher HDL (63 vs 56 mg/dL), and higher LDL (136 vs 113 mg/dL).
While the authors warned about the higher LDL, looking further we see that the total cholesterol-to-HDL radio remained the same after both diets at 3.4, and the TG:HDL ratio improved in the time-restricted eating group (1.5 vs 1.8). Therefore, even though LDL went up, overall lipid profiles improved during time-restricted eating.
Interestingly, the subjects reported increased hunger throughout the time they ate within a 4-hour window. But keep in mind this was a high-carbohydrate diet. Would it have been different on a low-carb diet? Clinical experience suggests that yes, they would have been less hungry, but we don't have comparative data.
So, it seems reasonable to extrapolate this data to OMAD, and predict that it may also provide the same or greater benefits. But we still don't know if the benefit remains for long-term, daily OMAD. Since we have hesitation about the daily use of OMAD, the lack of long-term data is concerning. That is where alternate-day fasting comes in.
Alternate-day fasting is essentially every-other-day OMAD. Eat normally for a day, then follow the OMAD pattern for a day. This addresses concerns about chronic caloric restriction because every other day is "normal" eating, alternating with a fasting or calorie-restricted day. One study compared ADF to chronic caloric restriction and found it was better tolerated and delivered similar benefits for weight loss and body composition. Another study in patients with type 2 diabetes showed that one day of consuming 500 calories followed by two days of normal eating produced HbA1c improvements similar to those observed during chronic caloric restriction.
While none of these studies definitively show OMAD is healthy and sustainable, we can reasonably extrapolate from the data and suggest that OMAD can likely be a part of a healthy, sustainable eating protocol.
"Best use" of OMAD
OMAD appears to be a powerful tool to help with weight loss and metabolic health. That said, we caution against chronic daily use of OMAD for all the reasons outlined above. Instead, for those who may benefit from more pronounced time-restricted eating, using OMAD one to three times per week, on non-consecutive days, could be an effective tool. This is not a science-based protocol with plenty of high-quality evidence, but is instead based on the information presented in this guide and on clinical experience.
Just remember, OMAD is not a license to eat whatever you want. What you eat for your one meal still matters. We recommend you stick with your low-carb plan on OMAD and non-OMAD days alike. In fact, clinical experience suggests that a well-formulated low-carb diet makes intermittent fasting and OMAD easier to do by reducing hunger and cravings. So, you can consider LCHF as your secret weapon to build your OMAD superpower.
Here is a sample week utilizing OMAD:
- Monday: eat two meals with 16:8 time-restricted eating, targeting 1,800 calories.
- Tuesday: OMAD, around 1,200 calories (assuming a standard 1,800-calorie intake). Aim for 30% protein (105 grams), 10 grams carbs and 104 grams fat. Some may find this volume challenging. If so, consider lengthening your eating window so that you eat a "snack" of nuts and cheese and then, an hour later, eat your full meal.
- Wednesday: eat two meals with 16:8 time-restricted eating, 1,800 calories
- Thursday: OMAD, similar to Tuesday
- Friday: eat two meals with 16:8 time-restricted eating, 1,800 calories
- Saturday: free day to eat how your social schedule dictates (just stay on your low-carb plan!)
- Sunday: OMAD, similar to Tuesday
OMAD meal plan
Full meal plan →
Summary
So, is OMAD a healthy and helpful tool for weight loss and metabolic improvements? Yes, it can be. But use it wisely and pay attention to your calorie and nutrient needs.
If you can incorporate it into a healthy pattern of time-restricted eating and low-carb nutrition, you may be well on your way to achieving your health and weight goals.
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