Why You Should Only Eat One Meal a Day (OMAD) with Caution

November 24, 2025 •

4 min read

According to a 2023 study published in the Journal of the Academy of Nutrition and Dietetics, skipping meals was linked to an increased risk of all-cause and cardiovascular disease mortality. This raises important questions about the one-meal-a-day (OMAD) approach, which is an extreme form of intermittent fasting.

Quick Summary

This article examines the reasons for and against adopting a one-meal-a-day diet, outlining its potential for weight loss and metabolic improvements alongside significant risks like nutrient deficiencies and high cholesterol. It provides a balanced perspective on OMAD, its comparison to other fasting methods, and offers expert guidance for consideration.

Key Points

Risks Outweigh Benefits: OMAD is an extreme fasting method with significant risks, including nutrient deficiencies, that often outweigh the potential benefits for many individuals.
Not for Everyone: This diet is not suitable for pregnant women, children, older adults, or those with underlying medical conditions like diabetes, and requires prior consultation with a healthcare provider.
Weight Loss Mechanism: OMAD can facilitate weight loss by inducing a calorie deficit and prompting the body to burn fat for energy during extended fasting periods.
Nutrient Density is Key: If you choose to attempt OMAD, it is vital to ensure your single meal is extremely nutrient-dense to prevent deficiencies.
Consider Alternatives: Less restrictive forms of intermittent fasting, like the 16/8 method, or standard calorie reduction are often more sustainable and safer for most people.
Focus on Sustainability: Long-term health and weight management are better achieved through balanced, sustainable lifestyle changes rather than extreme and potentially risky dietary patterns.

Understanding the One-Meal-a-Day (OMAD) Approach

The one-meal-a-day (OMAD) diet, also known as the 23:1 intermittent fasting method, involves fasting for 23 hours each day and consuming all daily calories within a single, typically one-hour, eating window. This approach is an intense form of intermittent fasting, popular for its simplicity and potential health advantages. While some find benefits like weight loss and improved metabolic markers, scientific evidence highlights considerable risks associated with OMAD.

Potential Benefits of the OMAD Diet

Certain benefits are associated with OMAD, though they are often linked to fasting in general. Restricting the eating window can lead to reduced calorie intake and potential weight loss. A 2022 study noted that limiting calories to a short evening period supported weight loss and increased fat burning during exercise. Extended fasting periods may also enhance metabolic health, potentially improving insulin sensitivity and blood sugar control, which could lower type 2 diabetes risk. Fasting can also trigger autophagy, a process of cellular repair linked to longevity. Some individuals report better focus during fasting, and the simplicity of one meal can streamline daily life.

Significant Risks and Concerns of the OMAD Diet

Despite potential benefits, the OMAD diet carries numerous risks, leading many healthcare professionals to caution against it, especially for long-term use. It is challenging to consume all necessary nutrients in a single meal, increasing the risk of deficiencies. The extended fasting can cause intense hunger, fatigue, and irritability, and may contribute to disordered eating patterns. Some research indicates that eating one meal a day can raise total and LDL cholesterol and increase blood pressure, potentially elevating cardiovascular risk. For individuals with conditions like diabetes, OMAD can cause dangerous blood sugar fluctuations. A study in 2023 linked eating one main meal daily to an increased risk of all-cause and cardiovascular disease mortality. In some cases, this extreme fasting might also lead to muscle mass loss.

OMAD vs. Other Intermittent Fasting Methods


Feature	OMAD (23:1)	16/8 Method	5:2 Diet
Fasting Period	23 hours daily	16 hours daily	2 non-consecutive days per week
Eating Window	1 hour daily	8 hours daily	5 days per week
Calorie Restriction	Significant daily deficit	Moderate daily deficit	Significant deficit on 2 days
Difficulty Level	High	Low to moderate	Low to moderate
Nutrient Intake	Difficult to achieve full range	More manageable across 8 hours	Easier on non-fasting days
Medical Consensus	Not widely recommended	Often supported as sustainable	Often supported as sustainable
Key Risk	Nutrient deficiency, binge eating	Less restrictive, easier adherence	Can lead to overconsumption on non-fasting days

How to Approach OMAD Safely

Proceeding with extreme caution is vital for anyone considering the OMAD diet. It is not appropriate for everyone, including pregnant or breastfeeding women, children, older adults, and those with pre-existing health conditions like diabetes. Consulting a healthcare provider before starting is essential. If attempting OMAD, prioritize a single meal rich in diverse, nutrient-dense whole foods to minimize deficiency risk. Monitor your body's response and stop if you experience negative symptoms. Exploring less extreme intermittent fasting methods or simple calorie restriction is often more beneficial and sustainable.

Conclusion

The OMAD diet, while seemingly appealing for its simplicity and potential for rapid weight loss, is an extreme approach with considerable health risks. While some fasting-related benefits exist, safer and more sustainable methods, such as the 16/8 intermittent fasting pattern, can achieve many of the same outcomes. Given the serious concerns regarding nutrient deficiencies, metabolic health impacts, and increased mortality risk, caution is imperative. For most individuals, achieving health and well-being through a balanced diet and sustainable lifestyle changes is a safer and more reliable path. Always consult a healthcare professional before implementing significant dietary changes.

Expert Takeaways on the OMAD Diet

Extreme Fasting: The OMAD diet, or 23:1, is one of the most extreme forms of intermittent fasting, requiring a 23-hour fast daily.
Potential for Weight Loss: By significantly reducing the eating window, OMAD can lead to a considerable calorie deficit, which may result in weight loss.
Risk of Nutrient Deficiencies: It is extremely challenging to consume all necessary nutrients in a single meal, raising the risk of malnutrition.
Not a Sustainable Plan: For most individuals, OMAD is not a sustainable long-term eating plan and may lead to negative physical and mental health consequences.
Consult a Professional: It is crucial to consult a healthcare provider before attempting the OMAD diet, especially for individuals with pre-existing medical conditions.
Alternative Options: Less restrictive and more sustainable eating patterns, such as the 16/8 method or simply reducing overall caloric intake, are often safer and more effective alternatives.

Frequently Asked Questions

Most healthcare professionals do not recommend following the OMAD diet long-term due to the risk of nutrient deficiencies, increased hunger, and potential negative impacts on metabolic health and cardiovascular risk factors.

You may lose weight on an OMAD diet due to a significant calorie deficit. However, this is not guaranteed, as some people may overeat during their single meal or experience a slowed metabolism, making it difficult to sustain weight loss.

If you follow an OMAD diet, your single meal should be as nutrient-dense as possible, including fruits, vegetables, lean protein, healthy fats, and whole grains to help prevent deficiencies.

The OMAD diet should be avoided by pregnant or breastfeeding women, children, teenagers, older adults, and individuals with a history of eating disorders or medical conditions like diabetes.

Common side effects include intense hunger, fatigue, low energy levels, irritability, dizziness, and difficulty concentrating, especially during the long fasting periods.

Some research suggests OMAD can negatively impact glucose regulation, causing higher fasting blood sugar and elevated cholesterol levels compared to more frequent eating patterns.

No, research indicates that OMAD is not necessarily more effective for weight loss than other, less extreme intermittent fasting methods like the 16/8 approach, and it carries greater risks.