What Is Meant by One Meal a Day (OMAD)?

January 1, 2026 •

3 min read

According to a 2022 study, restricting calorie intake to a small window led to body fat and weight loss in some healthy individuals. This reflects the core concept of what is meant by one meal a day, a restrictive form of intermittent fasting known as OMAD.

Quick Summary

One meal a day (OMAD) is an extreme intermittent fasting plan where all daily calories are consumed within a single hour, followed by a 23-hour fast. It creates a calorie deficit but presents significant health risks and may not be sustainable long-term for many people.

Key Points

Definition: One meal a day (OMAD) is an extreme form of intermittent fasting with a 23-hour fast and a 1-hour eating window.
Mechanism: It creates a calorie deficit and forces the body to burn stored fat, but it can be hard to meet daily nutritional needs.
Risks: Significant risks include nutrient deficiencies, potential metabolic disruptions (e.g., higher LDL cholesterol and blood pressure), and side effects like fatigue and irritability.
Sustainability: OMAD has a low sustainability rate and is not recommended as a long-term strategy for most people due to its extreme nature.
Precaution: Experts advise consulting a healthcare professional before starting, especially for individuals with health conditions or a history of eating disorders.
Focus: If attempting OMAD, prioritize a single, extremely nutrient-dense and balanced meal.

Understanding the One Meal a Day (OMAD) Concept

The practice of eating only one meal a day, known as OMAD, is an extreme version of intermittent fasting. It involves consuming all daily calories within a single, roughly one-hour eating window, followed by a 23-hour fast. During the fasting period, only non-caloric drinks like water, black coffee, or plain tea are permitted.

The main goal of OMAD is to create a calorie deficit to promote weight loss. The extended fasting also encourages the body to switch from burning glucose to burning stored fat, a metabolic state called ketosis.

How OMAD Differs from Other Fasting Methods

OMAD is more restrictive than other intermittent fasting methods like the 16:8 plan, which allows an 8-hour eating window. While some people might use OMAD occasionally, many health professionals advise against daily OMAD due to its extreme nature.

Potential Benefits of the OMAD Diet

Research on daily OMAD is limited, but proponents suggest potential benefits based on time-restricted eating principles. These include potential short-term weight loss due to a calorie deficit, a simpler eating schedule, and possible improvements in insulin sensitivity. Fasting can also trigger autophagy, a cellular repair process.

Significant Risks and Side Effects of OMAD

Daily OMAD carries substantial health risks that generally outweigh the potential benefits.

Health and Metabolic Concerns

It is difficult to get all necessary nutrients in one meal, increasing the risk of deficiencies. Studies suggest OMAD may increase total and LDL cholesterol and blood pressure. Eating one large meal, especially at night, might also lead to higher fasting blood sugar and elevated cortisol levels. Additionally, extreme calorie restriction can lead to muscle loss.

Side Effects and Sustainability Issues

Many individuals find OMAD hard to sustain due to side effects. These include intense hunger, cravings, fatigue, irritability, and dizziness from low blood sugar. OMAD can also pose social and practical challenges. High dropout rates for OMAD have been reported.

OMAD versus Other Intermittent Fasting Methods

Here is a comparison of OMAD and the 16:8 intermittent fasting method:


Feature	One Meal a Day (OMAD)	16:8 Intermittent Fasting	Resulting Health Implications
Fasting Window	23 hours	16 hours	Longer fasting in OMAD can lead to greater metabolic shifts, but also increased hunger and side effects.
Eating Window	1 hour	8 hours	A wider window in 16:8 allows for multiple, smaller meals, making it easier to consume adequate nutrients and avoid binge eating.
Nutrient Intake	Extremely difficult to achieve	Challenging but achievable	Daily OMAD significantly increases the risk of nutritional deficiencies due to the limited time to eat.
Sustainability	Low	High	Studies show much lower dropout rates and better long-term adherence for 16:8, as it is less restrictive.
Cardiovascular Risk	Elevated blood pressure and cholesterol reported.	Improved blood pressure and cholesterol levels in some studies.	OMAD's extreme nature poses higher cardiovascular risks compared to more moderate fasting.

Conclusion: Considering OMAD with Caution

What is meant by one meal a day is a highly restrictive fasting method. While it may offer some short-term benefits similar to less extreme diets, the significant risks like nutrient deficiencies, metabolic issues, and potential for disordered eating make it generally unsafe and unsustainable for long-term use. Healthcare professionals usually recommend less restrictive methods. It is vital to consult a healthcare provider before starting OMAD, especially with pre-existing conditions or a history of eating disorders. A balanced diet and less extreme fasting are often safer and more effective.

What to Eat During Your OMAD Meal

For those attempting OMAD under medical guidance, the single meal must be nutrient-dense. Focus on a balanced intake of lean protein, healthy fats, complex carbohydrates, and fiber-rich vegetables. Remember to stay hydrated with non-caloric drinks throughout the day.

Disclaimer: Always consult a healthcare provider or a registered dietitian before starting any restrictive diet, including OMAD.

Frequently Asked Questions

When you only eat one meal a day, you enter a prolonged fasting state where your body burns stored fat for energy. While this can lead to weight loss, it can also cause intense hunger, fatigue, irritability, dizziness, and nutritional deficiencies.

Eating one meal a day is generally not considered safe or sustainable for most people, especially over the long term. Risks include metabolic disruptions, elevated blood pressure and cholesterol, potential loss of muscle mass, and increased risk of disordered eating patterns.

Eating one meal a day can lead to weight loss by creating a significant calorie deficit. However, research shows it may not be more effective for long-term weight loss than other methods, and the restrictive nature often leads to rebound weight gain.

Common guidelines for the OMAD diet involve consuming all daily calories within a 1-hour window, fasting for the remaining 23 hours, only drinking zero-calorie beverages during the fast, and focusing on a single, nutrient-dense meal. More details can be found on {Link: BodySpec https://www.bodyspec.com/blog/post/omad_the_ultimate_guide_to_one_meal_a_day_eating}.

For most people, less extreme forms of intermittent fasting like the 16:8 method are considered safer and more sustainable. OMAD is more difficult to adhere to and carries higher health risks, including nutrient deficiency and metabolic issues.

During the 23-hour fasting window, you can drink zero-calorie beverages such as water, black coffee, or unflavored tea. Any drinks with calories, including diet soda or sweetened teas, will break the fast.

OMAD is not recommended for children, older adults, pregnant or breastfeeding women, and individuals with a history of eating disorders or health conditions like diabetes, kidney disease, or cardiovascular issues.