According to the science, no, it doesn’t and here’s why. The only fair way to assess the diet is to have groups eating the same number of calories, fats, proteins and carbohydrates but consumed over 1 meal, 2 meals or 3 meals per day and monitor the results.
There was virtually no difference between any of the groups as far as 24 hour fat oxidation or total caloric expenditure. The things that did differ were that the groups eating at least 2 or 3 meals per day had a much greater level of satiation.
Whereas in the one meal per day group the main complaints were those of hunger and extreme fullness after the one meal. So much so, that some participants akined it to having to stuff themselves with Thanksgiving dinner every single day.
They also complained of the blood sugar swings from eating such a large meal and then just wanting to sleep or even feeling as if they were going to pass out afterwards.
The results were that; with both calories and macronutrients remaining the same both groups had identical caloric expenditures and fat oxidation during the tests. All 3 groups lost nearly identical amounts of fat.
And since the fasting duration was for less than 24 hours, even the one meal per day group did not experience significant levels of autophagy.
In short, there were no statistically significant differences between the groups other than satiation.
Disclaimer: The following is for educational purposes only. We are not advocating a change in dietary, health or exercise protocols. Please seek the advice or council of your nutritionally educated health care practitioner prior to engaging in any dietary or exercise changes.
What Is An OMAD Diet?
The One Meal Per Day Diet or OMAD for short is a diet where the dieter only consumes food in a single sitting per day, as stated ‘for one meal’.
This is to say that whatever calories that person would have consumed during a normal 3 meal day they now consume all at one sitting.
The thoughts behind it are that A). Since you’re only consuming one meal you will be overly satisfied and full at the end of it, so you won’t even want to overeat.
This plan tends to backfire on most people, and they get overly hungry during the day and start just watching their clocks until they can put that first bite of food in their mouths.
B). The thought is that you’ll stimulate autophagy which would help to clear away old, damaged cells and repair broken ones. As we will discuss below this may not actually be the case.
C). They presume that it will be easier for you to reduce your overall calories. Whereas, in reality, most people use the OMAD diet as an excuse to eat foods they know are bad for them but taste great.
Is A One Meal A Day Diet Dangerous?
Yes, in several ways it is.
It could lead to diabetes pretty easily because you’re condensing all your calories into one meal which will drive your blood sugar through the roof in response to it.
This constant spiking of insulin is really not good for the body, it will take a toll pretty darn quickly which could lead to all the things that being diabetic bring with it such as, blindness, heart failure and stroke and that’s topping off obesity, decay of the extremities and more.
The diet also packs your digestive system to the brim with food at only one time per day. This over stuffing can cause digestive polyps, leaky gut syndrome and cancer.
Then, on top of all that, you don’t even get one of the main benefits that everyone is espousing.
Autophagy. When you abstain from eating for long enough you go into a state of self-eating, or autophagy. This is a way your body cleans up and repairs itself.
However, research indicates that you’d need to water fast for at least 24 hours straight to really enter that state. Because you eat every 20 hours or so, you never really get deep into it and start getting the big benefits.
Do the negatives outweigh the positives on OMAD? Keep reading because you have not yet even come close to discovering them all.
Can You Get All Your Nutrition With Just One Meal Per Day?
Yes, technically can. However, we would strongly advise against it.
You can, because you can pack one meal with over 2,000 calories and be sure to have vegetables, fruits, and then lots of high calorie foods to top off the caloric needs.
The challenge with this is digesting it all.
Just as one example: there are numerous studies that show that it’s not impossible, but certainly difficult to get all of your daily protein from just one serving.
So, what you’re asking your body to do is to fix everything in just a couple of hours after you eat and then go the rest of the day with no building blocks to work with at all.
Think about that in just common-sense terms.
It might more readily accomplish this if you have your one meal just an hour before bed so that you get the advantage of up to 70% of your daily growth hormone being secreted in the first one hour of REM sleep.
The problem is that growth hormone is not properly released in the presence of high insulin.
And the one thing we can all but guarantee you is that, when you eat all that food at once, you’re going to spike insulin like mad.
In fact, there are studies that show an insulin spike so huge that if a doctor tested you at just that moment in time, he would swear you were a diabetic.
In conclusion, sure you can get all your nutrition in just one meal. But, is it worth it?
Will The One Meal Per Day Diet Ruin Your Metabolism?
It sure can cause an upset in your natural circadian rhythm.
Quite likely never before in your lifetime have you ever consistently consumed only one meal per day, and so your metabolism is built around a completely different system.
While your metabolism may very well adapt over time there will be some considerable time elapsed before you’re dealing with it as if it were a natural course.
Then, if you ever wanted to go back to eating three square meals, then you’d have that massive adjustment back to that type of a metabolism.
The longer you’d been on one meal per day, the longer it would take to recover from it.
Would this actually ruin your metabolism?
No, not likely. However, it could set up a long-term battle to get your old metabolism back on track and running smoothly again.
Can The OMAD Diet Cause Constipation?
No, not likely, so long as you’re getting enough total daily fiber and drinking enough water throughout the day.
The vast majority of people who are constipated are so because their diets lack sufficient water and fiber.
Once you nail those two down you should be fine.
Now, if you think you’re just going to eat the Standard American Diet (SAD) while on OMAD and that will somehow magically fix you, then you are seriously deranged.
It’s not going to happen. The SAD eating will destroy your health, not build it up.
Then, combining that with stuffing all that garbage down your throat all at once is a recipe for disaster.
Can The One Meal A Day Diet Cause Diarrhea?
It certainly could in the short term while your body adjusts. However, unless you dramatically changed the foods you eat along with eating just once per day, then no, there really should not be an issue long term.
As stated, short-term eating all your food in just one meal will put stress on your digestive system that’s a near certainty. How that translates into your bowel movements is another thing entirely.
How Much Weight Can You Lose On OMAD In A Week Or A Month?
In truth, you’ll lose just as much as you would have lost on any other diet in a week or month. Here’s why. Eating all your daily calories in just one meal does not magically make you lose weight, sorry to have to be the bearer of bad news. The number of calories you reduce your overall diet by is the amount that you’ll lose.
If you were eating 2,000 calories of the Standard American Diet before you went one meal a day and you continue to eat the exact same way only you cram it in all in one sitting, you won’t lose anything at all. Many people actually find that they gain weight.
The reason being is that they are not using the calories efficiently all throughout the day, but instead dumping them all in at once, spiking the heck out of their insulin which actually causes them to store the excess as fat.
Let’s say you reduced your calories by 500, so you eat 1,500 calories per day instead of 2,000. You could lose up to 1 pound of fat per week. The reason is that 1 pound of fat equals 3,500 calories and reducing your calories by 500 for 7 days also equals 3,500.
If you continued to eat 1,500 per day for the month you could lose 1 pound per week time 4 weeks in the month means 4 pounds of fat loss for the month.
We want to be very clear. You could reduce your calories by 500 if you were eating 3 times per day or 6 times per day. The eating frequency of once per day just makes it easier for some people to adhere to it.
However, if the forums are any clue, the long term OMAD people have real problems eventually and have to get off of it at some point because they just can’t take it mentally anymore.
How Long Can You Stay On The One Meal A Day Diet?
Most people will stay on the diet for a short term to attempt to lose weight. If you research the Intermittent Fasting and diet forums online you’ll find that most people can’t seem to stick with the one meal per day plan for very long. It has a very low long term success rate from what dieters are saying about it.
Sure, you’re always going to hear from the people who just started it a week or two ago and it’s ‘changing their lives’. Those people tend to be very vocal. You don’t tend to hear too much from the people who quit, because most people don’t like to have to admit they quit something.
So, you start looking for comments from people who have gone over 1 month and they get pretty slim. Then looking for those who have gone 6 months gets to be almost nonexistent.
When you’re doing this kind of research you just have to be a bit of a sleuth.
On OMAD Can You Eat Anything Else For The Rest Of The Day?
No. You are confined to that one meal per day. Some people say it’s ok to have an apple or another piece of fruit a few hours before your one big meal. But this would defeat it in name and in purpose.
You’re supposed to only eat one meal so that you will find yourself hard pressed to overeat. You’re literally so stuffed that you have a really hard time finishing the food you’re supposed to eat, let alone any more than that.
Others say that it’s ok to have cream and sugar in your coffee if you’re into that. However, once again, this would defeat the purpose of limiting all your calories to just one eating window with the hopes of stimulating autophagy.
Is Two Meals Per Day Better Than OMAD?
According to several studies, consuming one meal for breakfast and one meal for an early dinner is far more satiating than consuming just one meal per day. Then, in truth, it’s mostly dependent on the total number of calories that you consume per day as far as what really gets you the results you are looking for.
If you can maintain a caloric deficit easier with one meal per day, than that might be best for you. If it’s easier with two meals per day, then that would (according to studies) be the way to go.
I.E. It’s all about the caloric deficit.