The "one meal a day" diet, also known as OMAD, is an extreme form of intermittent fasting that involves consuming all your daily calories in a single meal or a short window of time, typically one hour, and fasting for the remaining 23 hours. This eating pattern has gained popularity as a weight loss strategy and for its potential health benefits. However, it's essential to understand the potential benefits, risks, and how to implement it correctly.
Understanding the OMAD Diet
The OMAD diet is a type of intermittent fasting that restricts calorie consumption during a certain window of time. Eating one meal a day is a practice that many people swear by to lose weight and improve overall health. Although the content and timing of the meal will vary based on personal preference, people following an OMAD diet typically restrict their calorie intake to a single meal or a short window of time. The potential health benefits of OMAD are primarily related to fasting - restricting calorie intake during a set time period - and calorie restriction in general.
There are many types of intermittent fasting practices and multiple ways to implement OMAD. Examples include having just one meal and fasting for the rest of the day or having one meal and eating limited amounts of food during fasting periods. Some versions of this eating pattern allow a snack or two in addition to the one meal. However, some OMAD enthusiasts don’t consume anything containing calories during their fasting window and only consume calories during their chosen meal, which typically lasts an hour or so.
Potential Benefits of the OMAD Diet
Proponents of OMAD claim it can bring impressive health benefits, such as:
Weight Loss
Eating just one meal a day reduces calorie intake compared to consuming three meals, leading to effective and rapid weight loss. To lose weight, you must create an energy deficit. You can do this by either increasing the number of calories you burn or reducing your calorie intake. Calorie restriction, no matter how you achieve it, will lead to fat loss. People using the OMAD method are likely to lose weight simply because they’re taking in fewer overall calories than they typically would during a regular pattern of eating. However, it doesn’t seem to be any more effective than traditional methods of calorie restriction, such as reducing calorie intake at each meal.
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A 2017 data review involved gathering meal intake information from 50,660 adult Seventh-day Adventist Church members ages 30 years and older living in the United States and Canada. The research showed that those who consumed 1 or 2 meals per day had a yearly reduction in body mass index (BMI) compared to those who consumed 3 meals per day. It also showed that an overnight fast of 18 hours or more was associated with decreased body weight compared to shorter fasting windows. However, these weight loss benefits are related to intermittent fasting in general, not just the OMAD. Plus, extreme methods of fasting, such as OMAD, may lead to loss of lean body mass as well.
Simplified Meal Planning
With OMAD, there is no need to plan multiple meals throughout the day.
Increased Concentration and Productivity
Since the one-meal-a-day diet does not include lunch, it can eliminate the sluggishness of the body when digesting food for lunch.
Other Potential Health Benefits
Other health benefits related to fasting include the potential to reduce heart disease risk factors, decrease blood sugar, and reduce inflammation. Fasting may help reduce blood sugar and certain heart disease risk factors, including LDL “bad” cholesterol. Additionally, fasting may offer unique benefits that support a healthy nervous system. According to animal research, it may slow neurodegeneration and promote longevity.
Risks and Considerations
Despite the potential benefits, the OMAD diet is not suitable for everyone and presents several risks:
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Potential Adverse Effects
Although research has associated fasting and calorie restriction with a variety of health benefits, some evidence suggests that too much calorie restriction - which can include only consuming one meal a day - may do more harm than good. For example, an older study suggests that this extreme restriction may lead to increased total and LDL “bad” cholesterol and higher blood pressure levels compared to typical eating patterns or less extreme fasting methods.
Another older study involved middle-age healthy men and women who were of moderate weight and asked to eat meals at scheduled intervals but not restrict their calories. The research suggests that eating one meal per day may increase fasting blood sugar levels, delay the body’s response to insulin, and increase levels of the appetite-stimulating hormone ghrelin compared to eating three meals per day. This eating method may lead to extreme hunger.
Restricting calories to one meal a day may increase the chances of hypoglycemia, or low blood sugar, especially in those with type 2 diabetes.
Common Symptoms
In addition to these potential adverse effects, eating one meal a day can lead to symptoms, including:
- Nausea
- Dizziness
- Irritability
- Low energy
- Constipation
Loss of Lean Body Mass
This eating method may not be ideal for maintaining or building muscle mass. Loss of lean body mass is associated with an increased risk of metabolic diseases, such as type 2 diabetes, cardiovascular disease, or dyslipidemia.
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Not Suitable for Everyone
The OMAD diet is also not appropriate for many groups of people, including those who are pregnant or breastfeeding, children and teens, older adults, and people with eating disorders. The OMAD diet can be extremely dangerous for children and young adults who are hypoglycemic, have diabetes, obesity, or metabolic disorders. Moreover, this diet can also increase the risk of binge eating.
Risk of Nutrient Deficiency
Eating one meal a day is unlikely to give you the calories and nutrients your body needs to thrive unless carefully planned. Limiting intake to one meal per day can also lead to disordered eating tendencies, affect a person’s social life, and be extremely difficult for most people to stick to. What’s more, it can be very difficult to take in enough nutrients in one meal. This can lead to nutrient deficiencies, which can negatively affect your health and can lead to serious risks.
Potential for Overconsumption of Unhealthy Foods
Some people following the OMAD dietary pattern may likely overly consume highly processed, calorie-dense foods like fast food, pizza, doughnuts, and ice cream during their one meal. While these foods can fit into a balanced lifestyle, exclusively eating foods high in added sugar and other low nutrient ingredients will negatively affect your health in the long run.
How to Apply the OMAD Diet Safely
While OMAD may not be as harmful as some believe, it’s not suitable for everyone. It should not be practiced as a long-term eating habit over weeks or months. If you want to try fasting but are unsure about OMAD, consider a more manageable approach, like the 5:2 diet or the Warrior Diet. Occasionally eating one meal a day during busy periods can be a great way to challenge yourself and improve discipline in eating habits.
Consult a Nutritionist
To determine whether OMAD is suitable for you, consult a nutritionist for advice. Before starting any diet plan, you should consult with a nutrition expert for guidance.
Listen to Your Body
The key to success with OMAD-or any diet-is listening to your body. If OMAD causes severe negative effects on your health, discontinue the diet and opt for a more suitable approach.
Focus on Nutrient-Dense Foods
No matter the type of dietary pattern you choose, your intake should mostly consist of whole, nutrient-dense foods. If you do choose this eating pattern, it’s essential to ensure that you’re consuming a variety of nutritious foods, including:
- Fruits, such as berries, citrus fruits, and bananas
- Vegetables, such as kale, broccoli, cauliflower, asparagus, and peppers
- Starchy vegetables and grains, such as sweet potatoes, butternut squash, oats, quinoa, and barley
- Healthful fats, such as avocados, olive oil, and unsweetened coconut
- Legumes, such as peas, chickpeas, lentils, and black beans
- Seeds, nuts, and nut butters, such as cashews, macadamia nuts, almonds, and pumpkin seeds
- Dairy and plant-based alternative products, unsweetened yogurt, coconut milk, and cashew milk
- Protein sources, such as chicken, fish, tofu, and eggs
Limit highly processed foods, such as:
- Fast food
- Sugary baked goods
- White bread
- Sugary cereals
- Soda
- Chips
These foods offer little nutritional value, and eating them too often can lead to weight gain and increased disease risk.
Ensure Adequate Calorie Intake
If eating one meal a day, try to make meals as nutrient-dense as possible. These meals should deliver at least 1,200 calories, which can be difficult for some to ingest over a typical meal window.
Consider Increasing Eating Window
If you find it challenging to eat enough calories in one meal, consider increasing your eating window by an hour or so and splitting your meal into two smaller meals. This can help you get enough nutrients and calories without becoming overly full.
Potential Meal Ideas
Here are some nutritionally complete meal ideas that are likely to exceed 1,200 calories if portion sizes are large enough:
- Baked chicken with mashed sweet potatoes topped with butter and roasted broccoli with olive oil, followed by full fat Greek yogurt topped with berries, nuts, seeds, and honey.
- Grilled salmon topped with guacamole, brown rice and black bean salad, and roasted plantains, followed by fruit served with nut butter, hemp seeds, and coconut flakes.
- Egg omelet with goat cheese, avocado, and grilled vegetables cooked in coconut oil, crispy baked potato wedges, followed by a side of fruit dipped in dark chocolate and whipped cream.
Each meal should account for all food groups and include carbohydrates, fats, and proteins.
Avoid Long-Term Use
In general, OMAD is not a sustainable long-term diet and should not be used as a primary method for weight loss. Most people follow the OMAD pattern a few days a week, cycling it in with a normal dietary pattern or a less restrictive intermittent fasting regimen like the 16/8 method.
Why You Might Not Be Losing Weight on OMAD
If you are eating only one meal a day, you may find yourself overeating during your one meal if you are not mindful of your food intake. It’s important that your one meal is particularly balanced. With an increase in hunger, the temptation to overly eat highly processed, high carb foods may be harder to resist, leading to a net increase in calories, especially if you are not staying physically active.
OMAD and the 23-Hour Fast
This is a type of OMAD diet in which your one meal per day is restricted to a single hour and you eat nothing for the remainder of the day. Although fasting in general - including prolonged fasting - may benefit health in a number of ways, people can reach the same health benefits using much more sustainable methods. More sustainable eating plans include 16/8 intermittent fasting or simply following a healthful, lower calorie dietary plan if you’re currently eating in a surplus and want to promote weight loss. Most healthcare professionals advise against OMAD dietary patterns due to their extreme nature.