Thousands of years ago, the Ancient Romans ate one large meal per day around 4 PM.[*] In other words, they practiced something like OMAD.
The Romans believed it was healthy to eat this way, but were they right? Is the intermittent fasting (IF) protocol called OMAD good for you?
There isn’t much data to answer that specific question. But we do know that taking periodic food breaks (aka, intermittent fasting) is linked to a host of health benefits, from weight loss to gut health to improved insulin function.[*][*][*]
We also know that the Keto diet has many overlapping benefits to IF. Which is why you see a lot of folks doing OMAD plus Keto.
This article is a brief guide to OMAD, with special focus on how it pairs with Keto. You’ll learn what OMAD is, how to do it, potential health benefits, concerns, and some recipes to get you started.
Sound good? Let’s get into it.
What Is OMAD?
OMAD stands for one meal a day. When you practice OMAD, you eat all your daily calories in one sitting.
OMAD is a form of intermittent fasting, an eating regimen that involves taking regular breaks from food. These breaks generally last between 12 to 36 hours, depending who you talk to. Any fast longer than 36 hours is considered an extended fast.
The OMAD daily fast, on the other hand, lasts about 23 hours. The 24th hour… you eat!
OMAD Diet Rules
The main rule of OMAD is to eat one large meal per day, preferably while the sun is shining. (We’ll get to why meal timing matters in a minute).
A practical example will help. Let’s say you’re practicing OMAD, and you just finished your one big meal around 4 PM. You would then fast until bedtime, fast overnight, and fast until 3 or 4 PM the next day. Then it would be time to feast again.
How many calories should you eat on OMAD? That depends on your regular intake. If you typically eat 2000 calories, shoot for that number in your one meal, assuming it doesn’t disrupt your digestion.
People tend to eat fewer calories on OMAD, even without conscious restriction. A mild caloric deficit can be a sustainable weight loss strategy. A deep caloric deficit, however, won’t be.
Warrior Diet vs. OMAD
The Warrior Diet is a modified form of OMAD. But instead of one meal, you’re allowed 4 full hours each day to feed “like a warrior” who’s just made a kill. So 20 hours of fasting, 4 hours of feeding.
Alternate Day Fasting vs OMAD
There are two main types of intermittent fasting: Daily fasts and weekly fasts. OMAD is a daily fast, meaning you fast every day. Conversely, weekly fasts alternate fasting and feeding days. With alternate day fasting (ADF), you eat 0 to 25% of your normal calories (you fast) every other day.
Potential Benefits of OMAD
There isn’t much science on OMAD. Most researchers have looked at other forms of intermittent fasting.
- Weight loss
- Improved body composition (aka, less body fat)
- Better insulin sensitivity / blood sugar regulation
- Improved heart disease risk factors (lower triglycerides, lower blood pressure, lower cholesterol)
- Lower inflammation
- A healthy gut microbiome
Some of these benefits may be driven by circadian rhythm enhancement. Your circadian rhythm is your 24-hour wake / sleep cycle, and it regulates a large chunk of your genome.
Most intermittent fasting protocols (including OMAD) tend to favor daytime eating schedules. By not eating in the evening, you send the correct “sleep” signals to this clock—and this influences everything from blood glucose levels to inflammation. Eating during the day (and not at night) also appears to promote a more anti-inflammatory gut microbiome, at least in animals.[*]
But come on. Isn’t there any data on OMAD? Actually, there is.
One small study published in the American Journal of Clinical Nutrition found that when normal weight people ate one meal a day (compared to three), they had significant reductions in fat mass and cortisol, the stress hormone.[*] During the 8 weeks of OMAD, however, the participants also had higher blood pressure and LDL cholesterol, both markers of increased heart disease risk.
Another small study (n=15) used a similar setup. This time, normal weight men and women had higher fasting glucose levels (a negative sign for metabolic health) on OMAD than when they ate three meals per day.[*]
We already covered one concern with OMAD: That blood pressure, cholesterol, and blood glucose may rise in normal weight people, compared to three meals per day.[*] This concern is worth mentioning, but more data is needed to understand if this happens across all populations, and if it would show up in a larger sample. Would this be the case in an obese, diabetic cohort? We don’t know.
Another concern is the potential to undereat on OMAD. Depending on your metabolic needs, it may be difficult to cram enough calories into one meal.
And if you’re too low on calories, you will:
- Lose muscle
- Feel cold and hungry
- Be fatigued
One final concern? Eating a huge meal can tax your digestive system, causing symptoms such as gas, bloating, and acid reflux.
The key is to find a sweet spot: Not too few calories and not too much. If your gut can’t handle a meal that meets your caloric needs, consider a different fasting protocol.
OMAD on Keto
A low-carb Ketogenic diet pairs nicely with OMAD. When you eat a Keto diet, your body adapts to using fat for energy.
This fat-adaptation comes in handy during your daily fast. It keeps you humming along with smooth and steady energy.
The Keto diet can also curb cravings by reducing hunger hormones like ghrelin and neuropeptide Y.[*] Also helpful for going 23 hours without food.
OMAD Keto Meals
As we wrap up, here are several low-carb recipes for OMAD plus Keto. Scale up the portions to suit what your body needs. Remember: You’re only eating once per day!
Want more Keto recipes for OMAD? We’ve got thousands right here. Enjoy.
- Is OMAD an eating disorder? No. However, intermittent fasting regimens like OMAD and ADF are not recommended for those with anorexia, bulimia, or other eating disorders.
- When is the best time to eat on OMAD? Eating during the day benefits your wake / sleep cycle. Some evidence suggests that finishing up by 4 PM is ideal[*].
- How many calories should I eat on OMAD? Eat your normal calories. If you want to lose weight, a mild caloric deficit (~10% fewer calories) may be better suited to your goals.
- Will OMAD slow your metabolism? There’s no evidence that intermittent fasting slows your metabolism. But if you chronically restrict calories on OMAD, it’s a possibility.
- Why am I not losing weight with Keto and OMAD? You may be eating too many calories. Track your daily intakes using the Carb Manager app. Other areas to watch are sleep, exercise, and hidden carbs on Keto.
- Can you build muscle with Keto plus OMAD? Theoretically, yes. But it will be difficult to get enough calories and protein to fuel muscle growth on OMAD. There’s a reason bodybuilders are constantly eating!
- Do you have to eat Keto with OMAD? No, but eating Keto helps you fat-adapt and curb hunger while fasting.
- How much protein should you have with Keto plus OMAD? Aim to get 25-30% of your calories from protein. For a 2000 calorie meal, that’s 125-150 grams of protein.
There are multiple routes available when it comes to fasting and your program should be determined by your individual health needs. If OMAD does not feel like a good fit for you, consider starting with a more sustainable approach, increasing your fasting window if this feels appropriate. And if you are looking for extra support, why not use the Carb Manager IF tracker to help build your custom fasting schedule.
Please note that as with any significant diet or lifestyle change, we recommend working alongside a registered health professional, especially if you are currently on any prescribed medications or undergoing any medical treatments. Fasting is not appropriate for everyone and should be avoided by those with a history of eating disorders, pregnant and breastfeeding women, and anyone under 18.