Intermittent fasting involves alternating periods during which you eat, referred to as the eating window, with periods during which you don’t eat, while staying hydrated (unlike dry fasting).
In the context of the OMAD fast, it is a 24-hour fast. This 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 truly beneficial lifestyle for metabolic health? It’s not so easy to decide.
As a dietitian, I share with you several essential nutritional tips to maximize the benefits of this practice if you wish to adopt it, and its health advantages.
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OMAD: midday or evening?
What time to eat during the OMAD fast? It is a question that comes up very often. I advise you to keep it simple, according to your daily activities and lifestyle.
You can eat in the evening during the week after your long workdays and choose Sunday noon to share a meal with family, for example.
The only golden rule for this eating mode is to have only one meal a day, without time constraints.
Like any fast, the OMAD diet can produce results only if it is adapted to your lifestyle management.
If you are among those for whom this eating rhythm becomes natural and a source of well-being, OMAD in the long term is possible. Conversely, if you experience this approach as a struggle, it is 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 what you want. And that is what might seem appealing. As long as you stick to the same time each day to eat, the OMAD fast is without caloric restriction.
There are no forbidden foods during OMAD. However, I advise you to limit ultra-processed foods that are often high in calories but low in macro and micronutrients.
Since the number of meals is limited, the quality of food chosen is therefore important to meet your needs. Think of seasonal fruits and vegetables, whole grains, oilseeds, and vegetable oils.
Varied meals
I recommend making sure to vary your menus well, by eating different things every day.
First, so you don’t get bored! Then, to avoid missing out on essential nutrients, fiber, vitamins, and minerals.
Good hydration
Another essential point: make sure you hydrate well throughout the day. I recommend all calorie-free drinks: water, sparkling waters, infusions, tea, and coffee in reasonable quantities.
Can you lose weight with OMAD?
One of the main reasons people adopt the OMAD fast is weight loss. It makes sense; by limiting your calorie intake to just one meal per day, you naturally create a caloric deficit.
The practice of 24-hour fasting was compared with consuming three daily meals in this study, without caloric restriction.
The results over 16 weeks showed a reduction in fat mass and a slight increase in lean mass among participants in the OMAD group.
The OMAD weight loss was evaluated to be on average less than 2 kg, in a stable manner.
Another study conducted in 2022 concluded that one meal a day (in the evening in the study) reduces body weight. And allows for some metabolic flexibility during exercise through an increase in fat oxidation.
What are the links between OMAD and insulin sensitivity?
Insulin sensitivity means that your body reacts favorably to this hormone made by the pancreas and stimulated by blood sugar levels (glycemia).
People with impaired insulin sensitivity or insulin resistance are at higher risk of developing 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 in the cells. And mobilize its reserves to provide energy when it runs short during periods of deprivation.
What are the risks with OMAD?
Nutritional deficiencies
Like any diet with rules, I warn about the risk of a low-calorie diet. Although OMAD may offer health benefits, supplementation with multivitamins and omega-3 might be necessary.
Hunger
Another risk: hunger. It can be difficult to manage and require a lot of effort for some people.
Especially 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. Therefore, listen to your sensations.
Weight regain
Another possible inconvenience is of course the yo-yo effect. What happens when you start eating in a more conventional way?
Without nutritional education, I doubt its benefits in the long term.
What are the contraindications of OMAD fasting?
Fasting is not recommended for everyone. OMAD is contraindicated for pregnant and breastfeeding women, children, as well as elderly people.
Medical advice is essential before starting. If you are following certain medications that require specific timings or must be taken with food, precautions are necessary.
To be more cautious, if you have a condition, OMAD fasting should be supervised by your doctor.
To fast or not to fast? My health advice
Yes, fasting can present numerous benefits for metabolic health: improve digestion, physiological sensations, reduce inflammation…
Unfortunately, studies on the OMAD diet are limited. The claims generally rely on research concerning intermittent fasting and its many variations rather than on OMAD itself.
More perspective on medically-targeted fasting is, in my opinion, necessary before considering it as a miracle dietary protocol suitable for everyone.
If weight loss and insulin sensitivity in healthy individuals seem possible with OMAD, without your physical performance and muscle mass being affected, I remind you that other means exist.
Eating habits, hunger, and satiety can also improve with nutritional guidance, accompanied by a dietitian.
Regarding good health and weight results, regular physical activity combined with a balanced distribution of nutrients has proven effective.
I believe consuming all your daily calories in one meal should only be done if it fits a natural eating pattern. Ask yourself the question: Does OMAD bring you certain well-being? Or the exact opposite? Moreover, it must be part of a nutritional strategy to avoid lacking 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.
