Intermittent fasting involves alternating periods when you eat, known as the eating window, with periods when you don’t eat, while staying hydrated (unlike dry fasting).
In the context of OMAD fasting, it is a 24-hour fast. That means eating once a day and giving yourself an eating window of about 30 minutes to 1 hour.
Studies highlight its benefits for weight loss. Is it just another weight-loss diet or a true lifestyle beneficial for metabolic health? Not so simple to decide.
As a dietitian, I share with you several essential nutritional tips to maximize the benefits of this practice if you want to adopt it, and its health benefits.
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OMAD: midday or evening?
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 lifestyle.
You can eat in the evening during the week after your long workdays and choose Sunday lunchtime to share a meal with your family, for example.
The only golden rule for this eating pattern is to eat only one meal per day, with no time constraints.
Like any fast, the OMAD diet can produce results only 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. If, on the other hand, 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 food
In theory, you are free to eat whatever you want. And that’s what can seem appealing. As long as you stick to the same schedule each day for eating, OMAD fasting is not calorie-restricted.
There is no food forbidden during OMAD. However, I recommend limiting ultra-processed foods, which are often high in calories but low in macro- and micronutrients.
Because the number of meals is limited, the quality of the foods you choose is important to meet your needs. Think of seasonal fruits and vegetables, whole grains, nuts and vegetable oils.
Varied meals
I also recommend that you vary your meals by 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 well hydrated throughout the day. I recommend all calorie-free beverages: water, sparkling water, herbal 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 caloric intake to a single meal per day, you naturally create a calorie deficit.
The practice of 24-hour fasting has been 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, and remained relatively stable.
Another study conducted in 2022 concludes that a single meal per day (in the evening in the study) reduces body weight and allows some metabolic flexibility during exercise thanks to an increase in fat oxidation.
What are the links between OMAD and insulin sensitivity?
Insulin sensitivity means your body responds favorably to this hormone produced by the pancreas and released in response to the blood sugar level (blood glucose).
People with impaired insulin sensitivity or insulin resistance have a higher risk of developing type 2 diabetes or metabolic syndrome.
Many researchers have observed better glucose utilization during 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
As with any diet that has rules, I warn about the risk of a calorie-poor diet. Although OMAD may offer health benefits, supplementation with multivitamins and omega-3s may be necessary.
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 pay attention to how you feel.
Weight regain
Another possible drawback, of course, is the yo-yo effect. What happens when you (re)eat 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.
To fast or not? My health advice
Yes, fasting can offer many benefits for metabolic health: improving digestion, physiological responses, and reducing inflammation…
Unfortunately, studies on the OMAD diet are limited. Claims generally rely on research on intermittent fasting and its many variations rather than on OMAD itself.
More perspective on medically supervised fasting is, in my opinion, necessary before considering it a miraculous dietary protocol suitable for everyone.
If weight loss and improved insulin sensitivity in healthy people seem possible with OMAD, without your physical performance and muscle mass suffering, I should remind you that other options exist.
Eating habits, hunger and satiety can also improve with nutritional counseling, accompanied by a dietitian.
When it comes to good health and weight outcomes, the practice of regular physical activity combined with a balanced distribution of nutrients has proven effective.
I think consuming all 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 certain sense of well-being? Or quite the opposite? Moreover, it needs to fit into 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.
