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Dietary Essentials

The Science Behind The OMAD Diet – Benefits And Drawbacks

- Written By

DR Maheen Sohail , BDS

Updated on

This article is based on scientific evidence, written by experts and fact checked by experts. Our team of experts strive to be objective, unbiased, honest and to present both sides of the argument. This article contains scientific references. Read more about our process.


In today’s world, where dietary patterns constantly evolve, the One Meal a Day diet has captured the attention of many people seeking an alternative approach to weight management and improved health. OMAD diet has impressed many individuals with promises of weight loss, improved metabolism, and potential health benefits. The concept of the one meal a day diet is simple yet intriguing: restrict your daily eating to just one meal, fasting for the remaining hours. While the OMAD diet has achieved a dedicated following and numerous success stories, its scientific underpinnings, and potential benefits and drawbacks warrant a closer examination.

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What is OMAD Diet?

The One Meal a Day (OMAD) diet is intermittent fasting, where individuals restrict their daily eating to just one meal, typically consumed within a specific time window, and fast for the remaining hours of the day. This eating pattern involves an extended fasting period, often around 23 hours, followed by a single meal. People who follow this diet believe that this extended fasting period promotes the body’s fat stores for energy, leading to weight loss—additionally, prolonged fasting results in other potential health benefits, which we will explore further.

Example of an OMAD Diet Schedule

Fasting Period: 23 hours

Eating Window: 1 hour

Here’s how a typical day might look for someone following the OMAD diet

7:00 AM: Wake up and start the fasting period.

11:00 AM: Stay hydrated with water, herbal tea, or black coffee during fasting.

6:00 PM: Begin the eating window with a balanced, nutrient-dense meal.

7:00 PM: Conclude the meal and begin the fasting period again.

During the one-hour eating window, the individual would consume all their daily calories, nutrients, and sustenance. The meal should ideally include a mix of proteins, healthy fats, complex carbohydrates, and a variety of vegetables and fruits to ensure a balanced intake of essential nutrients.

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Example of an OMAD Diet Meal

Grilled chicken salad with quinoa and avocado

Grilled chicken breast for protein.

Mixed greens, tomatoes, and cucumbers for fiber and vitamins.

Quinoa for complex carbohydrates and additional protein.

Avocado for healthy fats and added nutrients.

Olive oil and balsamic vinegar for dressing.

While this example provides a balanced meal, it’s important to note that the OMAD diet’s success and safety depend on proper meal planning, nutrient intake, and individualized considerations. Consulting with a healthcare professional or registered dietitian before embarking on this eating pattern is highly recommended, especially if you have preexisting health conditions or unique nutritional requirements.

Health Benefits of the OMAD Diet

The One Meal a Day (OMAD) diet has gained attention for several potential advantages. It’s important to note that individual experiences can vary, and scientific research on the one meal a day diet is still developing.

1) Weight Loss

One of the primary reasons individuals choose the OMAD diet is its potential to aid in weight loss. The prolonged fasting period creates a calorie deficit, which, over time, can reduce body weight. The diet’s impact on insulin levels and metabolism may also contribute to fat loss.

2) Metabolic Benefits

Some research suggests that intermittent fasting, including the one meal a day diet, may positively affect metabolism, including increased fat oxidation and potential improvements in various metabolic markers.

3) Convenience

The OMAD diet’s structure simplifies eating decisions. For some individuals, the simplicity of eating just one meal a day aligns with their lifestyle and schedule, making it easier to adhere to the diet in the long run.

4) Improved Insulin Sensitivity

Fasting periods, like those in the OMAD diet, may enhance insulin sensitivity. This means the body becomes more responsive to insulin, potentially reducing the risk of type 2 diabetes and improving blood sugar control. Fasting periods give the body a chance to lower insulin levels, allowing cells to become more responsive to the hormone.

5) Cellular Repair

Fasting triggers a process known as autophagy, where the body breaks down and recycles damaged cells and cellular components. This cellular repair process contributes to overall health and reduces the risk of various diseases.

6) Enhanced Mental Clarity

Some individuals report improved mental clarity, focus, and alertness during fasting. This phenomenon might be linked to ketosis, a metabolic state in which the body uses ketones, produced from fat breakdown, as an alternative energy source for the brain.

7) Discipline

The OMAD diet can foster discipline and mindful eating. Individuals may become more aware of their food choices and portion sizes with a limited eating window.

8) Savings

Consuming one meal a day might reduce food expenses as the overall quantity of food consumed decreases.

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The Drawbacks of OMAD Diet

While the OMAD diet offers potential advantages, it also has several disadvantages and risks. Considering these factors before adopting the one meal a day diet as your eating pattern is essential. Here are some of the drawbacks:

1) Nutrient Deficiency

Consuming all your daily nutrients in just one meal can make it challenging to meet your daily recommended intake of vitamins, minerals, and other essential nutrients. This can lead to nutrient deficiencies over time, negatively impacting your overall health. OMAD diet poses challenges in meeting daily nutritional requirements. Individuals need to carefully plan their meals to ensure they receive adequate vitamins, minerals, and macronutrients.

2) Risk of Overeating

With a limited eating window, overeating can occur during one meal. This could offset the calorie deficit created during fasting and hinder weight loss goals. It’s crucial to practice portion control and choose nutrient-dense foods.

3) Muscle Loss

Prolonged fasting, combined with inadequate protein intake, can lead to muscle breakdown, mainly if protein intake is insufficient. Muscle preservation can be a concern for those aiming to improve body composition.

4) Energy Levels

Some individuals may experience low energy levels, especially during fasting. This could impact daily activities, work, and exercise performance.

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5) Hormonal Imbalances

Rapid changes in eating patterns, such as those imposed by the OMAD diet, can disrupt hormonal balance. This might particularly affect women, potentially leading to irregular menstrual cycles and hormonal disturbances.

6) Social Isolation

Adhering strictly to the OMAD diet can make sharing meals with family and friends challenging. This social isolation around eating times could impact your emotional well-being and social interactions.

7) Digestive Issues

Consuming a day’s worth of food in a single meal might overwhelm the digestive system, leading to discomfort, bloating, and other digestive issues.

8) Potential for Eating Disorders

The rigid structure of the OMAD diet could trigger or exacerbate disordered eating patterns, especially in individuals prone to eating disorders or with a history of disordered eating.

9) Lack of Long-Term Research

While some short-term research suggests potential benefits of intermittent fasting, including the OMAD diet, there needs to be more long-term research to understand its effects on health and sustainability fully.

10) Unsuitable for Certain Populations

The OMAD diet may not be suitable for pregnant individuals, breastfeeding mothers, growing adolescents, athletes with high energy requirements, and individuals with certain medical conditions. These populations have unique nutritional needs that may not be met with a restricted eating pattern.

11) Difficulty in Adherence

The strictness of the OMAD diet may make it challenging for some individuals to adhere to it over the long term. This could result in cycles of strict adherence followed by periods of overeating, potentially leading to frustration and a lack of sustainable results.

12) Lack of Enjoyment

Food is often associated with pleasure and enjoyment. Limiting eating to a single meal might diminish the joy of food and eating experiences.

Who Should Avoid OMAD Diet?

It’s essential to recognize that the OMAD diet, like any dietary approach, is only sometimes suitable for some. Age, sex, activity level, underlying health conditions, and personal goals must be considered before starting an eating pattern. Consulting with a healthcare professional or registered dietitian is crucial to determine if the one meal a day diet aligns with an individual’s needs and receive proper implementation guidance. 

Weight and Health Status: Some persons might initially benefit from the one meal a day diet due to the calorie deficit it creates. However, this type of fasting might not be appropriate for those with a healthy weight or underweight individuals. It could lead to nutrient deficiencies and other health issues.

Metabolic Conditions: While the OMAD diet’s potential to improve insulin sensitivity could benefit individuals with prediabetes or type 2 diabetes, it’s imperative to approach this diet under medical supervision. Rapid changes in eating patterns and calorie intake could impact blood sugar levels and necessitate medication adjustments.

Nutrient Requirements: Certain groups, such as pregnant individuals, growing adolescents, and breastfeeding mothers, have elevated nutrient needs. The one meal a day diet’s limited eating window might not provide adequate nourishment for these populations, potentially affecting their health and their developing child.

Athletes and Active Individuals: Those who engage in regular physical activity require sufficient energy and nutrients to support their workouts, recovery, and overall performance. The compressed eating window of the OMAD diet might hinder their ability to meet these demands adequately.

Gastrointestinal Issues: Individuals with gastrointestinal disorders or sensitivities might find it challenging to consume a day’s worth of nutrients within a single meal. This could exacerbate digestive issues and potentially lead to discomfort.


The amount of weight you can lose on the OMAD diet in a week varies depending on factors like your starting weight, metabolism, and adherence. While some individuals may experience rapid initial weight loss due to the calorie deficit, losing 1-2 pounds (0.45-0.9 kg) per week is a standard guideline for safe and sustainable weight loss. However, individual results can differ, and it’s important to prioritize health and balanced nutrition over rapid weight loss.

The number of calories you consume on the OMAD diet depends on your goals, metabolism, and activity level. While it’s recommended to consult a healthcare professional, a typical OMAD meal may range from 1,000 to 2,500 calories. Balance and nutrient density are vital to meet nutritional needs within your chosen calorie range.

Yes, you can drink coffee on the OMAD diet, preferably without added sugars or high-calorie additives. Black coffee, without cream or sugar, is famous as it contains minimal calories and may help suppress appetite during fasting. Remember to stay hydrated as well.

The claim that the OMAD diet detoxes the body needs more scientific consensus. While fasting periods might support natural detoxification processes, the body’s organs primarily handle detoxification. The OMAD diet’s potential benefits are more related to calorie reduction, possible weight loss, improved insulin sensitivity, and other metabolic effects rather than direct detoxification.

The optimal timing for One Meal a Day (OMAD) varies based on personal preferences and lifestyle. Common choices include an evening meal for social reasons, lunchtime for active afternoons, late afternoon for digestion, or morning for those adapting well. Consult a healthcare professional to determine what suits you best.

the bottom line

While the OMAD diet holds promise regarding weight loss and potential health benefits, its suitability is daily. The diet’s rigid eating pattern, extended fasting window, and potential for nutrient deficiencies and health risks make it essential for individuals to approach it with caution and awareness. Seeking professional guidance, especially from registered dietitians and healthcare providers, is necessary before starting the one meal a day diet, particularly for those with preexisting medical conditions, special nutritional requirements, or a history of disordered eating. Safety should always be a priority when considering any dietary approach, and individual well-being should guide all healthy decisions.

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