Can You Eat a Big Meal Once a Day? A Nutrition Diet Deep Dive

October 9, 2025 •

5 min read

While the one-meal-a-day (OMAD) diet has gained popularity, some studies, including a 2023 review, have linked meal skipping to an increased risk of mortality. So, can you eat a big meal once a day safely, and is it a sustainable approach to a healthy nutrition diet?

Quick Summary

This article explores the one-meal-a-day (OMAD) diet, detailing its metabolic effects, including potential short-term weight loss and increased fat burning. It also addresses significant drawbacks such as nutrient deficiencies, blood pressure and cholesterol changes, blood sugar fluctuations, and the risk of developing disordered eating patterns.

Key Points

Risks Outweigh Benefits: For most people, the potential risks of nutrient deficiencies, metabolic disruptions, and psychological distress associated with OMAD are greater than its benefits.
Nutrient Deficiency Concern: It is extremely difficult to meet all daily nutritional requirements for vitamins, minerals, and fiber within a single one-hour eating window.
Metabolic Impact: Studies have shown that consuming one large meal a day can negatively affect blood pressure, cholesterol, and blood sugar regulation.
Unsustainable Practice: OMAD is an extreme and often unsustainable diet that can lead to fatigue, hunger, irritability, and disordered eating patterns.
Safer Alternatives Exist: Less restrictive intermittent fasting methods, like 16:8, can provide similar health benefits with fewer risks and better long-term adherence.
Consult a Professional: Medical supervision from a healthcare provider or registered dietitian is strongly recommended before attempting any extreme dietary pattern like OMAD.

Understanding the One Meal a Day (OMAD) Diet

OMAD, a form of intermittent fasting, involves condensing all of your daily calorie and nutrient intake into a single meal, typically eaten within a one-hour window. This practice is a more extreme version of fasting methods like the 16:8 diet, which allows for an eight-hour eating window. The core principle of OMAD is to extend the body's fasting state, triggering a metabolic switch to burn stored fat for energy once glucose is depleted. While appealing due to its simplicity, the feasibility and long-term health implications of the OMAD diet are widely debated by nutrition experts.

The Potential Benefits of Extended Fasting

Proponents of the OMAD diet often cite benefits associated with intermittent fasting in general. It is important to distinguish that these benefits are not exclusive to OMAD and are often achievable with less extreme fasting methods.

Weight Loss: By restricting calorie intake to a small window, individuals often consume fewer total calories, leading to a calorie deficit and subsequent weight loss. Some studies show it can lead to a reduction in body fat.
Improved Insulin Sensitivity: Periods of fasting can give the pancreas a rest from producing insulin, potentially leading to improved insulin sensitivity. Some research on intermittent fasting has shown beneficial effects on blood sugar levels.
Enhanced Fat Oxidation: After glycogen stores are depleted from fasting, the body enters a metabolic state called ketosis, where it begins burning stored fat for fuel. A small 2022 study on lean individuals found that eating one meal per day in the evening increased fat oxidation during exercise.
Cellular Repair: Fasting can induce a process called autophagy, where the body's cells are recycled and repaired. This is a general benefit of fasting and not specific to OMAD.
Simplified Meal Planning: For some, the OMAD schedule simplifies daily routines by requiring only one meal to be planned and prepared, reducing the time and mental effort spent on food.

Significant Risks and Drawbacks

Despite the perceived advantages, medical experts generally advise caution or against the OMAD diet due to several significant health risks, especially over the long term.

Nutritional Deficiencies: It is extremely challenging to consume all necessary vitamins, minerals, protein, and fiber in a single meal. This can lead to nutritional deficiencies over time, impacting bone density, immune function, and overall health.
Metabolic Disruptions: Studies have shown that consuming one large, infrequent meal can put a strain on the metabolic system. Research has indicated that OMAD may increase fasting blood sugar, LDL (bad) cholesterol, and blood pressure in healthy individuals.
Blood Sugar Fluctuations: Prolonged fasting can cause low blood sugar (hypoglycemia), especially in the initial stages. The subsequent large meal can cause a rapid spike in blood sugar, which is particularly dangerous for individuals with diabetes.
Increased Mortality Risk: A 2023 study published in the Journal of the Academy of Nutrition and Dietetics linked eating only one meal a day with a higher risk of all-cause and cardiovascular disease mortality.
Side Effects: Common side effects include fatigue, dizziness, irritability, intense hunger, and difficulty concentrating due to low energy levels.
Risk of Disordered Eating: The highly restrictive nature of OMAD can trigger or worsen disordered eating behaviors, such as binge-eating, and can create an unhealthy psychological relationship with food.

OMAD vs. Other Intermittent Fasting Methods

When considering intermittent fasting, it is helpful to compare the most extreme method (OMAD) with a more moderate and widely accepted alternative, such as the 16:8 method. This table highlights key differences.


Feature	One Meal a Day (OMAD)	16:8 Intermittent Fasting
Eating Window	1-2 hours	8 hours
Fasting Window	22-23 hours	16 hours
Nutrient Intake	Very difficult to meet daily needs in one meal, high risk of deficiency.	More manageable to achieve balanced nutrition across multiple meals.
Metabolic Impact	Higher risk of blood sugar spikes, cholesterol increases, and blood pressure changes.	Generally linked to positive metabolic benefits without extreme swings.
Side Effects	More common and severe (fatigue, hunger, irritability) due to extended fasting.	Generally milder and easier to manage.
Sustainability	Low; high dropout rates reported due to extreme nature.	High; more flexible and easier to integrate into social life and routine.
Population Suitability	Not recommended for most people, especially those with health conditions.	Suitable for most healthy adults, with fewer contraindications.

Is a Single Large Meal a Sustainable and Healthy Option?

For most individuals, relying on a single, large daily meal is not a sustainable or nutritionally sound strategy for long-term health. The practical challenges of fitting all required calories and nutrients into one sitting, coupled with the mental and physical side effects, make it difficult to maintain. The restrictive nature of OMAD can create a preoccupation with food and may lead to a cycle of intense hunger followed by overeating.

For those drawn to the simplicity or potential benefits of fasting, a less extreme method like the 16:8 model offers a safer and more manageable approach. It allows for a more flexible schedule and multiple meals, making it easier to achieve nutritional balance and sustain long-term adherence.

How to Approach OMAD Safely (If at All)

Before considering OMAD, it is crucial to consult a healthcare professional or registered dietitian, especially if you have any pre-existing health conditions. If you choose to proceed, a gradual transition from a less restrictive fasting method is recommended.

Prioritize Nutrient Density: Your single meal must be meticulously planned to include a wide variety of whole foods, such as lean proteins, healthy fats, complex carbohydrates, and plenty of vegetables, to maximize nutrient intake.
Focus on Hydration: Drink plenty of water, black coffee, or herbal tea throughout the day to stay hydrated and manage hunger.
Listen to Your Body: Pay close attention to persistent fatigue, irritability, or other adverse symptoms. These are signals that this eating pattern may not be right for you and should prompt a return to a more balanced approach.

Conclusion

While the concept of eating one big meal a day has superficial appeal, the potential risks for nutrient deficiency, metabolic issues, and long-term health complications often outweigh the benefits, particularly when compared to less restrictive intermittent fasting methods. Ultimately, for a durable and healthy nutrition diet, a balanced and sustainable eating pattern with adequate nutrient distribution is a much safer and more effective strategy for most people.

Healthline provides a comprehensive overview of the OMAD diet, including its benefits and risks.

Frequently Asked Questions

The main risks include potential nutritional deficiencies, negative metabolic changes such as higher cholesterol and blood pressure, and increased risks of blood sugar fluctuations, fatigue, and developing disordered eating behaviors.

While some studies show weight loss with OMAD, often due to a significant calorie deficit, it is not shown to be more effective than more moderate and sustainable methods of calorie restriction or intermittent fasting. The initial weight loss may also include water weight.

The OMAD diet is not recommended for children, teenagers, pregnant or breastfeeding women, older adults, or individuals with a history of eating disorders or conditions like diabetes and metabolic disorders.

To create a nutritionally dense single meal, focus on a balance of lean protein, healthy fats, complex carbohydrates, and a wide variety of vegetables. Supplementation may be necessary, and professional guidance is strongly advised.

Common side effects include intense hunger, fatigue, irritability, dizziness, and constipation. These symptoms are often more severe in the initial stages as the body adjusts to the extended fasting period.

OMAD is an extreme form of intermittent fasting that restricts eating to a very small window, typically one hour. Less restrictive methods, like the 16:8 diet, allow for a much longer eating window, which is generally considered safer, more flexible, and more sustainable.

Prolonged and extreme fasting can slow down your metabolism as a survival mechanism. While some temporary metabolic benefits like increased fat oxidation have been noted in short-term studies, the long-term effects of OMAD on metabolism are a concern.