Can I eat all my calories in one meal?
Have you been experimenting with different diets? Are you looking into different ways to stay healthy? Maybe you’re curious about what eating habits will help you lose weight or feel better.
Whatever the reason, you may have asked yourself: can I eat all my calories in one meal?
In short, it’s not recommended. The one meal a day or OMAD diet is an extreme type of intermittent fasting (IF). It’s not practical for most people as it’s difficult to eat enough calories and get enough nutrients in one sitting. It can also be stressful for your body to adjust from three meals a day plus snacks to only one meal a day.
One study found that people consuming one meal a day were significantly hungrier than those eating three meals a day (Stote et al., 2007). Further, they experienced increased blood pressure, cholesterol, and lower cortisol levels. Low cortisol can cause fatigue or dizziness.
There are other effective intermittent fasting methods with fewer drawbacks than OMAD. These include the 16:8 method, 5:2 method, and alternate-day fasting.
The OMAD diet is not recommended for children and teens, seniors, people with eating disorders, chronic health issues, or if you’re pregnant. Anyone whose body, for whatever reason needs more nutrients, should steer clear of the OMAD diet.
What is 16:8 fasting?
16:8 fasting is an eating pattern that involves fasting for 16 hours and eating unrestricted for eight hours.
What is 5:2 intermittent fasting?
5:2 intermittent fasting involves eating unrestricted for five days out of seven and about 20 to 25% of your daily calories for the remaining two. The two fasting days should not be consecutive. Instead, space out those days so you can remain energized.
What is alternate day fasting?
Alternate day fasting is an eating pattern that involves eating unrestricted one day and fasting the next. Some people choose to not eat anything on fasting days. If you choose not to eat anything, you can still drink zero-calorie beverages such as water or tea. Alternate day fasting is sometimes called the 4:3 approach since, in one week, you eat unrestricted for four days and restricted for three days.
You can also eat between 20 and 25% of your daily calories if fasting completely doesn’t work for you.
These approaches, unlike the one meal a day (OMAD) diet, are time-restricted instead of meal-restricted. This means they limit what times of day you can eat rather than the number of meals you can eat.
For most people, time-restricted fasting (TRF) is easier to adapt to since you can eat whatever you’d like while not fasting. So, TRF approaches are much more popular than the OMAD diet.
Research shows that TRF reduces fasting glucose and fasting insulin in overweight or obese people (Nowosad & Sujka, 2021). Reduced fasting glucose and insulin, in turn, reduce the risk of diabetes.
Note: Fasting glucose is a measurement of your glucose levels after about 8 hours of fasting. And fasting insulin is a measurement of your insulin levels after about 8 hours of fasting.
TRF doesn’t only promote weight loss among overweight and obese people. The 16:8 approach (a type of TRF) promotes weight loss among male athletes too, according to a study in the Journal of Translational Medicine (Moro et al., 2016).
Interestingly, these athletes retained their muscle mass throughout the study – even while fasting.
That’s quite difficult to achieve with an approach like the OMAD diet, where you pack all your nutrients and calories into one meal. But the OMAD diet isn’t as heavily researched as other intermittent fasting approaches.
This comprehensive study on fasting and weight loss doesn’t even consider OMAD as an IF method (Patterson et al., 2015). There are plenty of studies out there linking other intermittent fasting approaches to weight loss (Tinsley & La Bounty, 2015). Even overweight adults with asthma lose weight thanks to IF (Johnson et al., 2007).
One study shows that intermittent fasting has differing effects on non-obese vs. overweight and obese individuals (Harvie & Howell, 2017).
Among overweight and obese individuals, IF curbed binge eating, reduced depression, and improved body image, according to this study.
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But, non-obese individuals experienced increased hunger, had trouble concentrating, and worried about over-eating on unregulated days, among other effects.
This study alone doesn’t prove that you should avoid intermittent fasting altogether if you are non-obese. Or that it will work well for all overweight and obese individuals.
But you should be aware of the potentially adverse effects. Know that regardless of your weight, fasting can have a significant impact on your body, especially if you haven’t done it before. It can take time to adjust and become comfortable with any intermittent fasting approach.
Keep in mind that intermittent fasting isn’t the only way to lose weight. You can also reduce your calorie intake every day, which is called continuous energy restriction, or CER.
Several studies have shown that CER is just as effective as intermittent fasting (Rynders et al., 2019; Headland et al., 2020). If you want a little more data, here’s another study (Harvie et al., 2011).
Continuous energy restriction (CER) involves cutting daily calories by 15% to 60% per day (Headland et al., 2020). You don’t fast at all. The more you cut your daily calories, the more difficult it’ll be to sustain the CER diet.
Whether you choose CER or IER depends on your eating habits and comfort while dieting, among other factors.
If you decide to try the OMAD diet…
...consult a doctor before you start. Consider trying OMAD one day at a time or a couple of times a week to start. Jumping from three meals a day to one meal a day for a full week will be a big shock to your body.
Some people like to increase their eating window so they don’t have to eat a ton of food per day in a short period. You might take two hours instead of one to eat and split your meal into two smaller meals.
I’m aware at that point you’re not eating one meal in a day. But it can be a good strategy to get used to the OMAD diet.
You can also mix and match certain fasting methods depending on what works best for you. But you still need to be getting enough nutrients. So again, consult a nutritionist or doctor before trying out the OMAD diet.
Do what’s best for you.
Hopefully you found this article on calories and fasting helpful. Remember that every person is different. So the diet your friend uses may not work for you. Talk to a doctor or nutritionist to nail down a personalized diet plan. Fasting isn’t necessary, but it can be beneficial for some people.
Thanks for stopping by our blog. If you want to dive deeper into any research I cited in this article, check out the references below. Or take a look at the related articles for more helpful information.
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References
Harvie, M., & Howell, A. (2017). Potential benefits and harms of intermittent energy restriction and intermittent fasting amongst obese, overweight and normal weight subjects - A narrative review of human and animal evidence. Behavioral Sciences (Basel, Switzerland), 7(1), 4. https://doi.org/10.3390/bs7010004
Harvie M. N., Pegington, M., Mattson, M. P., Frystyk, J., Dillon, B., Evans, G., Cuzick, J., Jebb, S. A., Martin, B., Cutler, R. G., Son, T. G., Maudsley, S., Carlson, O. D., Egan, J. M., Flyvbjerg, A., & Howell, A. (2011). The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: A randomized trial in young overweight women. International Journal of Obesity (Lond), 35(5), 714-27. doi: 10.1038/ijo.2010.171
Headland, M. L., Clifton, P. M. & Keogh, J. B. (2020). Impact of intermittent vs. continuous energy restriction on weight and cardiometabolic factors: A 12-month follow-up. International Journal of Obesity, 44, 1236–1242. https://doi.org/10.1038/s41366-020-0525-7
Johnson, J. B., Summer, W., Cutler, R. G., Martin, B., Hyun, D. H., Dixit, V. D., Pearson, M., Nassar, M., Telljohann, R., Maudsley, S., Carlson, O., John, S., Laub, D. R., & Mattson, M. P. (2007). Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radical Biology & Medicine, 42(5), 665–674. https://doi.org/10.1016/j.freeradbiomed.2006.12.005
Moro T., Tinsley, G., Bianco, A., Marcolin, G., Pacelli, Q. F., Battaglia, G., Palma, A., Gentil, P., Neri, M., & Paoli, A. (2016). Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. Journal of Translational Medicine, 14, 290. https://doi.org/10.1186/s12967-016-1044-0
Nowosad, K. & Sujka, M. (2021). Effect of various types of intermittent fasting (IF) on weight loss and improvement of diabetic parameters in human. Current Nutrition Reports, 10, 146-154. https://doi.org/10.1007/s13668-021-00353-5
Patterson, R. E., Laughlin, G. A., LaCroix, A. Z., Hartman, S. J., Natarajan, L., Senger, C. M., Martínez, M. E., Villaseñor, A., Sears, D. D., Marinac, C. R., & Gallo, L. C. (2015). Intermittent fasting and human metabolic health. Journal of the Academy of Nutrition and Dietetics, 115(8), 1203–1212. https://doi.org/10.1016/j.jand.2015.02.018
Rynders, C. A., Thomas, E. A., Zaman, A., Pan, Z., Catenacci, V. A., & Melanson, E. L. (2019). Effectiveness of intermittent fasting and time-restricted feeding compared to continuous energy restriction for weight loss. Nutrients, 11(10), 2442. https://doi.org/10.3390/nu11102442
Stote, K. S., Baer, D. J., Spears, K., Paul, D. R., Harris, G. K., Rumpler, W. V., Strycula, P., Najjar, S. S., Ferrucci, L., Ingram, D. K., Longo, D. L., & Mattson, M. P. (2007). A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. The American Journal of Clinical Nutrition, 85(4), 981-988. https://doi.org/10.1093/ajcn/85.4.981
Tinsley, G. M., and La Bounty, P. M. (2015). Effects of intermittent fasting on body composition and clinical health markers in humans. Nutrition Reviews, 73(10), 661-74. doi: 10.1093/nutrit/nuv041
Can I eat all my calories in one meal?
One study found that people consuming one meal a day were significantly hungrier than those eating three meals a day (Stote et al., 2007). Further, they experienced increased blood pressure, cholesterol, and lower cortisol levels. Low cortisol can cause fatigue or dizziness.
There are other effective intermittent fasting methods with fewer drawbacks than OMAD. These include the 16:8 method, 5:2 method, and alternate-day fasting.
The OMAD diet is not recommended for children and teens, seniors, people with eating disorders, chronic health issues, or if you’re pregnant. Anyone whose body, for whatever reason needs more nutrients, should steer clear of the OMAD diet.