Intermittent fasting consists of alternating periods during which you eat, called the eating window, with periods during which you do not eat, while staying hydrated (unlike dry fasting).
In the context of OMAD fasting, it is a 24-hour fast. This means eating once a day and allowing yourself an eating window of about 30 minutes to 1 hour.
Studies highlight its benefits for weight loss. Is it yet another weight-loss diet or a genuine lifestyle beneficial for metabolic health? It’s not so simple to decide.
En tant que diététicienne, je partage avec vous plusieurs conseils nutritionnels essentiels pour maximiser les bienfaits de cette pratique si vous désirez l’adopter, et ses intérêts santé.
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OMAD: lunch or dinner?
At what time to eat during OMAD fasting? It’s a question that comes up very often. I recommend keeping it as simple as possible, based on your daily activities and your lifestyle.
You can eat in the evening during the week after your long workdays and choose Sunday at midday, for example, to share a meal with your family.
The only golden rule for this eating pattern is to have just one meal per day, with no time constraints.
As with any fast, the OMAD diet will only yield results if it is adapted to your lifestyle.
If you are among those for whom this eating rhythm becomes natural and a source of well-being, long-term OMAD is possible. Conversely, if you experience this approach as a struggle, it’s better to consider other methods.
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What to eat during the OMAD diet?
Quantity and quality of foods
In theory, you are free to eat whatever you want. And that’s part of its appeal. As long as you maintain the same schedule each day for eating, OMAD fasting is without calorie restriction.
There is no forbidden food during OMAD. However, I recommend limiting ultra-processed foods that are often high in calories but low in macro- and micronutrients.
With the number of meals being limited, the quality of the chosen foods is therefore important to meet your needs. Think of seasonal fruits and vegetables, whole grains, nuts and vegetable oils.
Varied meals
I also recommend varying your meals, eating different things each day.
First, so you don’t get bored! Then, so you don’t lack essential nutrients, fiber, vitamins, and minerals.
Proper hydration
Another important point: stay adequately hydrated throughout the day. I recommend all calorie-free beverages: water, sparkling water, infusions, tea, and coffee in moderation.
Can you lose weight with OMAD?
One of the main reasons people adopt OMAD fasting is weight loss. It makes sense: by limiting your calorie intake to one meal per day, you naturally create a calorie deficit.
The practice of 24-hour fasting was compared with consuming three daily meals in this study, without calorie restriction.
Results over 16 weeks showed a reduction in fat mass and a slight increase in lean mass among participants in the OMAD group.
OMAD weight loss was estimated at less than 2 kg on average, consistently.
Une autre étude réalisée en 2022 conclut qu’un seul repas par jour (le soir dans l’étude) réduit le poids corporel. Et permet une certaine flexibilité métabolique pendant l’exercice grâce à une augmentation de l’oxydation des graisses.
What are the links between OMAD and insulin sensitivity?
The insulin sensitivity means your body responds favorably to this hormone produced by the pancreas and whose secretion is stimulated by the blood sugar level (glycemia).
People with impaired insulin sensitivity or insulin resistance are at higher risk of developing a type 2 diabetes or metabolic syndrome.
Many researchers have observed an improved glucose utilization during the practice of a 20-hour intermittent fast.
The body would adapt more to better distribute glucose into the cells. And mobilize its reserves to provide energy when it becomes scarce during periods of deprivation.
What are the risks with OMAD?
Nutritional deficiencies
Comme tout régime avec des règles, j’alerte sur le risque d’une alimentation pauvre en calories. Bien qu’OMAD puisse offrir des avantages santé, une supplémentation en multivitamines et en oméga-3 peut être nécessaire.
Hunger
Another risk: hunger. It can be difficult to manage and require a lot of effort for some people.
Notably in cases of eating disorders, OMAD is strongly discouraged.
Headaches
Headaches can sometimes be associated with the fasting state, more specifically related to ketosis, in cases of sleep disturbances, stress, anxiety, or dehydration. So listen to your body.
Weight regain
Another possible downside is, of course, the yo-yo. What happens when you (re)start eating in a more conventional way?
Without nutritional education, I doubt its long-term benefits.
What are the contraindications to OMAD fasting?
Fasting is not recommended for everyone. OMAD is contraindicated in pregnant and breastfeeding women, children, and the elderly.
Medical advice is essential before you start. If you are taking certain medications that require precise timing or must be taken with a meal, precautions should be taken.
To be on the safe side, if you suffer from a medical condition, OMAD fasting should be supervised by your doctor.
Jeûner ou non ? Mes conseils santé
Yes, fasting can offer numerous benefits for metabolic health: improving digestion, physiological sensations, reducing inflammation…
Unfortunately, the studies on the OMAD diet are limited. Claims generally rely on research into intermittent fasting and its many variations rather than on OMAD itself.
In my opinion, more long-term data on medically supervised fasting is needed before considering it a miracle diet protocol suitable for everyone.
While weight loss and improved insulin sensitivity in healthy people may be possible with OMAD, without negatively affecting your physical performance and muscle mass, I should remind you that other options exist.
Eating habits, hunger and satiety can also improve with nutritional counseling provided by a dietitian.
For good health and weight outcomes, regular physical activity combined with a balanced distribution of nutrients has proven effective.
I think consuming all of your daily calories in a single meal should only be done if it fits a natural eating pattern. Ask yourself: does OMAD bring you a sense of well-being? Or quite the opposite? It also needs to be part of a nutritional strategy so you don’t miss out on anything.
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Sources and scientific studies
- Kim S Stote, David J Baer, Karen Spears, David R Paul, G Keith Harris, William V Rumpler, Pilar Strycula, Samer S Najjar, Luigi Ferrucci, Donald K Ingram, Dan L Longo, Mark P Mattson, 2007. A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults.
- Emma C E Meessen, Håvard Andresen, Thomas van Barneveld, Anne van Riel, Egil I Johansen, Anders J Kolnes, E Marleen Kemper, Steven W M Olde Damink, Frank G Schaap, Johannes A Romijn, Jørgen Jensen, Maarten R Soeters, 2022. Differential Effects of One Meal per Day in the Evening on Metabolic Health and Physical Performance in Lean Individuals.
- N, Halberg, et al. 1985. Effect of Intermittent Fasting and Refeeding on Insulin Action in Healthy Men.
