Alternate Day Fasting and OMAD are two advanced intermittent fasting methods. They both provide similar health benefits, and they both have pros and cons. While the fasting time is longer with Alternate Day Fasting, it may be more difficult to get sufficient nutrients with OMAD
Disclaimer: Alternate Day Fasting and OMAD are two advanced versions of intermittent fasting. The article discusses these methods from a scientific perspective but does not represent medical advice. You should consult your doctor before starting intermittent fasting, especially when you have an underlying health condition or take medications.
There are many different methods of intermittent fasting. Two popular ones are Alternate Day Fasting (ADF) and One-Meal-A-Day (OMAD). Both include quite long fasting times and hence, are not very beginner-friendly.
However, they provide many benefits for experienced fasters. So what is the difference between the two, and which one is better?
Let’s first have a closer look at both methods.
As the name suggests, you fast every second day when following ADF. On your fasting days, you don’t consume any calories. On eating days, however, you can eat whatever you like and how much you want.
It is, however, recommended to eat 2-3 meals on the eating days and to avoid snacking. With this approach, you usually achieve a fasting time of at least 36 hours (for example, from 8 pm dinner on day 1 until 8 am breakfast two days later).
Since 36 hours is a long time and, for most people, not easy to accomplish, many people choose to follow a modified version of ADF. With modified ADF, you can consume around 500 kcal on your fasting day.
You can learn more about ADF in a separate article on this topic.
When following OMAD, you eat only once per day. This meal can consist of multiple courses and is usually eaten within a time window of 1-2 hours.
However, some people extend the meal even further and allow themselves an eating window of up to four hours. In this case, OMAD is identical to 20/4 intermittent fasting.
You can freely choose the time of the meal. However, most people choose to have their meal in the evening. This has mainly practical reasons since an extended meal during the day interferes with most work schedules.
Technically, you now know how Alternate Day Fasting and OMAD work. So, which one is better?
Let’s have a closer look at the pros of both methods.
With ADF, you don’t eat for an entire day. This means that the fasting time is around 50% longer than with OMAD.
Fasting stimulates certain physiological processes. But for these processes to start, you need to fast for a specific amount of time.
One important process is autophagy, a vital recycling program responsible for many health benefits of intermittent fasting. Exactly when autophagy starts in an individual is very personal because it depends on many factors such as age, sex, comorbidities, and physical activity.
Research suggests that it starts around 18 hours after the last meal for average people. However, it may take longer for some people, and autophagy also increases with time. That means the longer you fast, the more autophagy is induced.
Because the fasting time is longer with ADF, it is more potent in inducing autophagy.
Another crucial process is ketosis. During ketosis, the liver turns fat into ketone bodies, which are an excellent energy source. Even the brain can use ketones; it loves them, in fact.
Ketosis makes it easy to access your fat storage and, therefore, facilitates weight (or better fat) loss.
Additionally, keep in mind that ketone bodies are also anti-inflammatory. For this reason, ketosis provides many health benefits.
Most people reach ketosis with OMAD. But it isn’t maintained for long since the daily meal interrupts the process (assuming you’re not following a ketogenic diet).
ADF gives you much more time to reach ketosis, and it is deeper (meaning more ketone bodies are produced) because it is maintained for longer.
Your body needs many essential nutrients such as vitamins, minerals, protein, and essential fatty acids. One problem with OMAD is that it can be difficult to get sufficient nutrients with this one meal. For this reason, OMAD is not sustainable long-term for some people.
Although the fasting time is longer with ADF, you also have more time to eat. When you decide to eat 3 meals on your eating day, you can eat much more within two days than with OMAD and which allows you to take in more essential nutrients.
ADF is a very advanced intermittent fasting method and not easy to follow for most people. Even OMAD is quite advanced, but the fasting time is much shorter. With some intermittent fasting experience, most people manage to follow OMAD without too much struggle.
You can practice OMAD when you have to take medications with food, assuming that you don’t have to take them more than once a day. You just have to adapt your eating schedule to your medication schedule.
However, this is not possible when following ADF. Never skip any prescribed medications because of intermittent fasting. There are plenty of intermittent fasting methods that are compatible with taking medications, such as 12-hour fasting or 16/8 fasting.
Intermittent fasting methods with long fasting times are usually better for weight loss than shorter ones. The body simply has more time to access fat storage.
Because Alternate Day Fasting and OMAD both include long fasting times, they are both very effective for weight loss.
The fasting time with Alternate Day Fasting is longer–does that mean that it is more effective for weight loss? Not necessarily. With ADF, you have a very long uninterrupted fast. With OMAD, on the other hand, you have a very long fast every day. In total, the fasting time is longer with OMAD.
There are no studies comparing Alternate Day Fasting vs. OMAD side-by-side. But they are likely very similar when it comes to weight loss.
ADF and OMAD are both advanced intermittent fasting methods, and are definitely not for everyone. OMAD is easier to follow than ADF. One advantage of ADF is that ketosis and autophagy are induced more potently. It is also easier to get sufficient nutrients.
It is not possible to say definitively which of these two methods is better. It very much depends on your circumstances and personal preferences.
All intermittent fasting methods provide substantial health benefits–intermittent fasting promotes weight loss, reduces insulin resistance, improves cardiovascular health, decreases inflammation, and potentially extends lifespan. In the end, the most important thing is that you find a method that you find easy to follow and that suits your lifestyle.
If you want to learn more about intermittent fasting, we invite you to join our intermittent fasting community for women only.
1. Martinez-Lopez N, Tarabra E, Toledo M, et al. System-wide Benefits of Intermeal Fasting by Autophagy. Cell Metab. Dec 5 2017;26(6):856-871 e5. doi:10.1016/j.cmet.2017.09.020
2. Jamshed H, Beyl RA, Della Manna DL, Yang ES, Ravussin E, Peterson CM. Early Time-Restricted Feeding Improves 24-Hour Glucose Levels and Affects Markers of the Circadian Clock, Aging, and Autophagy in Humans. Nutrients. May 30 2019;11(6)doi:10.3390/nu11061234
3. Foster DW. Studies in the ketosis of fasting. J Clin Invest. Aug 1967;46(8):1283-96. doi:10.1172/JCI105621
4. Courchesne-Loyer A, Croteau E, Castellano CA, St-Pierre V, Hennebelle M, Cunnane SC. Inverse relationship between brain glucose and ketone metabolism in adults during short-term moderate dietary ketosis: A dual tracer quantitative positron emission tomography study. J Cereb Blood Flow Metab. Jul 2017;37(7):2485-2493. doi:10.1177/0271678X16669366
5. Masood W, Annamaraju P, Uppaluri KR. Ketogenic Diet. StatPearls. 2021.
6. Youm YH, Nguyen KY, Grant RW, et al. The ketone metabolite beta-hydroxybutyrate blocks NLRP3 inflammasome-mediated inflammatory disease. Nat Med. Mar 2015;21(3):263-9. doi:10.1038/nm.3804
7. de Cabo R, Mattson MP. Effects of Intermittent Fasting on Health, Aging, and Disease. N Engl J Med. Dec 26 2019;381(26):2541-2551. doi:10.1056/NEJMra1905136
