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One Meal a Day (OMAD)

One meal a day is a version of intermittent fasting. In this article, we break down everything you need to know about it.
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Summary

Breakfast, snack, lunch, snack, dinner, snack/dessert. Is this how your normal day looks like? Most people are eating from the moment they wake up until right before they go to sleep – this usually translates to about 16 hours a day!

The chronic overconsumption of food is a main reason why we are seeing an increase in metabolic diseases.

Written by
Christine Richardson, PhD
Clinical Project Manager at Becton Dickinson

Intermittent fasting is a dietary pattern that many people are choosing to follow to try to improve their overall health. While there are many forms of intermittent fasting, one version is called One Meal a Day or OMAD. Many people will quickly tell you that OMAD is a form of disordered eating, but this is because we have been groomed to believe that eating 3 meals a day, plus snacks, is the healthiest way to eat.

The idea that eating 3 meals a day is the healthiest meal pattern is not founded in any science. In fact, many studies suggest that eating fewer meals a day can help improve some aspects of overall health, especially weight loss (1–3).


What is OMAD ?


OMAD is definitely one of the more “extreme” versions of intermittent fasting because it consists of consuming all calories in a 1-2 hour window. In order to follow this diet well, you must also try to be consistent with when you choose to eat. In other words, you eat during the same hours every day. Some people may choose to wake up and eat a large breakfast and fast for the rest of the day, whereas others will fast throughout the day and eat later around dinner time. 


You also need to be more diligent about consuming enough calories. Food is meant to fuel the body and depriving your body of energy for an extended period of time can lead to certain health complications.

While the idea of not consuming enough calories relative to the amount you burn has been mostly studied in athletes, it is very well established that not consuming enough calories can lead to negative health consequences such as disruptions to hormones, low bone mass, impaired immunity, chronic fatigue, and more (4–6).

In addition, your body adjusts to the lower amount of energy it is receiving and will change certain bodily processes to conserve weight. In other words, your body prevents itself from losing any body fat (7).


The bottom line is, if you decide to try an OMAD diet, make sure you are eating enough calories to fuel your body. There may be an adjustment period, where your body is adapting to this new way of eating so consuming about 2000 calories in one meal at first may be impossible. But those that follow an OMAD diet claim that over time, your body adapts and eating one very calorie-dense meal becomes possible. 


Benefits

Woman with oranges.

There are various benefits to following an OMAD diet. 


For starters, the rules are relatively simple. Pick a 1-2 hours that you choose to be your eating window. The key is to be consistent with your meal timing. Pretty simple right?


You don’t need to limit your calories. Most diets require people to restrict their caloric intake. With OMAD, you do not need to restrict your calories. In fact, you might have the opposite problem where you might not be eating enough calories. Try tracking your caloric intake for a few days to make sure you are getting enough calories for your sex, height, weight, and activity level. There are many online calorie intake calculators you can use to give you an estimate. 


Extending your fast by such a great amount will really help you achieve all of the health benefits associated with intermittent fasting such as fat loss, decreased damage to DNA, anti-aging properties, and improvements in various disease risk factors (1,8–13). You will probably see results quickly and this might help keep you motivated to stick with it.


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Cons

You might feel very hungry at first. There is going to be a learning curve with such an extreme diet that your body is going to have to adjust to. This should only last 1-2 weeks; but keep in mind that it should be temporary. Try drinking water and tea to help curve your hunger cravings. However, if you start to feel light-headed, dizzy, or faint, you should probably eat something.


A big potential con to OMAD is sustainability. Is this a diet that you can realistically do long-term? This is definitely something to consider when choosing the right dietary plan. A good strategy might be to play around with a few different types of intermittent fasting and see which one is the best fit for you. There is no wrong answer. 


The Bottom Line


Most people are constantly eating throughout the day, which may not be beneficial for your health. 


Some forms of intermittent fasting, such as OMAD, may help you achieve various goals you have regarding your health. OMAD may seem like an extreme variation of intermittent fasting but, if done correctly, you may find yourself feeling better and happier. However, if you have any questions about OMAD, you may want to discuss this dietary pattern with your doctor.  


References:

1. Paoli A, Tinsley G, Bianco A, Moro T. The influence of meal frequency and timing on health in humans: The role of fasting. Nutrients. MDPI AG; 2019. 

2. Kahleova H, Lloren JI, Mashchak A, Hill M, Fraser GE. Meal frequency and timing are associatedwith changes in body mass index in Adventist Health Study 2. J Nutr [Internet]. American Society for Nutrition; 2017 [cited 2021 May 5];147:1722–8. Available from: https://pubmed.ncbi.nlm.nih.gov/28701389/

3. Mattson MP, Allison DB, Fontana L, Harvie M, Longo VD, Malaisse WJ, Mosley M, Notterpek L, Ravussin E, Scheer FAJL, et al. Meal frequency and timing in health and disease. Proc Natl Acad Sci U S A [Internet]. National Academy of Sciences; 2014 [cited 2021 May 6];111:16647–53. Available from: /pmc/articles/PMC4250148/

4. Wasserfurth P, Palmowski J, Hahn A, Krüger K. Reasons for and Consequences of Low Energy Availability in Female and Male Athletes: Social Environment, Adaptations, and Prevention [Internet]. Sports Medicine - Open. Springer; 2020 [cited 2021 May 5]. Available from: /pmc/articles/PMC7483688/

5. Sundgot-Borgen J, Garthe I. Elite athletes in aesthetic and Olympic weight-class sports and the challenge of body weight and body composition. J Sports Sci. 2011;29. 

6. Ackerman KE, Holtzman B, Cooper KM, Flynn EF, Bruinvels G, Tenforde AS, Popp KL, Simpkin AJ, Parziale AL. Low energy availability surrogates correlate with health and performance consequences of Relative Energy Deficiency in Sport. Br J Sports Med [Internet]. BMJ Publishing Group; 2019 [cited 2020 Aug 16];53:628–33. Available from: https://bjsm.bmj.com/content/53/10/628

7. Benton D, Young HA. Reducing Calorie Intake May Not Help You Lose Body Weight. Perspect Psychol Sci [Internet]. SAGE Publications Inc.; 2017 [cited 2020 Jun 28];12:703–14. Available from: /pmc/articles/PMC5639963/?report=abstract

8. Malinowski B, Zalewska K, Węsierska A, Sokołowska MM, Socha M, Liczner G, Pawlak-Osińska K, Wiciński M. Intermittent fasting in cardiovascular disorders—an overview. Nutrients. MDPI AG; 2019. 

9. Anton SD, Moehl K, Donahoo WT, Marosi K, Lee SA, Mainous AG, Leeuwenburgh C, Mattson MP. Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity. Blackwell Publishing Inc.; 2018. p. 254–68. 

10. Longo VD, Mattson MP. Fasting: Molecular mechanisms and clinical applications. Cell Metabolism. NIH Public Access; 2014. p. 181–92. 

11. Stockman MC, Thomas D, Burke J, Apovian CM. Intermittent Fasting: Is the Wait Worth the Weight? Current obesity reports. NIH Public Access; 2018. p. 172–85. 

12. Jamshed H, Beyl RA, Manna DLD, 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. MDPI AG; 2019;11. 

13. Mattson MP, Longo VD, Harvie M. Impact of intermittent fasting on health and disease processes. Ageing Research Reviews. Elsevier Ireland Ltd; 2017. p. 46–58. 


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