Do you gain more weight by eating once a day? The surprising link between OMAD and weight control

October 9, 2025 •

5 min read

A 2022 study found that reducing meal frequency to a single meal per day lowered body mass in participants, challenging the common misconception: do you gain more weight by eating once a day?. The answer is more complex and depends on overall calorie balance rather than meal timing alone.

Quick Summary

Eating one meal a day does not automatically cause weight gain, as weight change is determined by total caloric intake versus expenditure. While it can aid weight loss through calorie reduction, potential risks include nutrient deficiencies, fatigue, muscle loss, and binge eating.

Key Points

Caloric Balance Is Key: Weight gain or loss is primarily determined by the total calories consumed versus burned, not the number of meals per day.
OMAD Can Lead to Weight Loss: By naturally restricting caloric intake, eating once a day can help create the necessary calorie deficit for weight loss.
Risks Include Nutritional Deficiencies: A single meal makes it extremely difficult to meet all daily nutrient requirements, potentially leading to deficiencies.
Beware of Binge Eating: Prolonged fasting can increase hunger, potentially leading to overeating or bingeing during the single eating window.
Muscle Loss is a Risk: Extended fasting combined with inadequate protein can cause loss of muscle mass, which negatively impacts metabolism.
Not for Everyone: OMAD is not recommended for individuals with diabetes, eating disorders, or other underlying health conditions.
Sustainability is Often Low: Due to its restrictive nature and potential side effects, OMAD can be difficult to maintain in the long term.

The Calorie Equation: Debunking the Meal Frequency Myth

The fundamental principle of weight management is the concept of energy balance—the relationship between the calories you consume and the calories your body burns. At its core, weight gain occurs when you consistently consume more calories than your body uses (a caloric surplus), and weight loss happens when you burn more calories than you consume (a caloric deficit). Meal timing, including whether you eat once or multiple times a day, is secondary to this core equation. If you consume 2,500 calories in a single meal, but your body only needs 2,000 to maintain its weight, you will gain weight, regardless of when you ate. Conversely, if you eat a 1,500-calorie meal but burn 2,000 calories, you will lose weight.

The idea that eating once a day automatically slows your metabolism, causing you to gain weight, has been widely debated and largely refuted in modern nutritional science. While very prolonged fasting periods can trigger metabolic changes, the body is highly adaptable. Short-term fasting, as seen in the OMAD diet, often shifts the body's fuel source from glucose to fat stores, increasing fat oxidation. However, this adaptation does not automatically guarantee weight loss; the overall calorie balance is still the deciding factor.

The One Meal A Day (OMAD) Diet: What It Is and How It Works

The OMAD diet is an extreme form of intermittent fasting that restricts all daily caloric intake to a single, typically one-hour, eating window. The remaining 23 hours of the day are spent fasting, during which only calorie-free beverages like water, tea, or coffee are allowed. Proponents of OMAD are often attracted to its simplicity, as it eliminates the need for frequent meal planning and preparation.

Potential Benefits of the OMAD Diet

Fat Loss: Research, including a small 2022 study, has indicated that eating a single large evening meal can lead to a reduction in body mass and an increase in fat oxidation. Participants showed lower total body fat, although not always significant total weight loss.
Improved Insulin Sensitivity: Fasting periods can lead to lower and more stable insulin levels, which can improve insulin sensitivity over time.
Simplicity and Time-Saving: The structured approach can simplify life for some, reducing time spent on cooking and meal prep.

The Health Risks of Eating Once a Day

While some benefits exist, OMAD comes with significant health risks that make it unsuitable for many individuals. It's crucial to consider these drawbacks before adopting such a restrictive diet.

Nutrient Deficiencies: It is exceptionally challenging to consume all the essential vitamins, minerals, fiber, and protein your body needs in a single meal, even if it is very large. Long-term deficiencies can lead to severe health problems, including compromised bone density and a weakened immune system.
Risk of Binge Eating: The prolonged fasting period can lead to intense hunger, increasing the likelihood of overeating or binge eating during the one-hour window. This can negate any potential calorie-saving benefits and lead to weight gain.
Muscle Mass Loss: Extended fasting, particularly without adequate protein intake, can lead to muscle atrophy. Loss of lean muscle mass can slow metabolism, making future weight management more difficult.
Blood Sugar Instability: For individuals with diabetes or insulin sensitivity, OMAD poses significant risks due to potential blood sugar fluctuations, including hypoglycemia (low blood sugar) during fasting and hyperglycemia (high blood sugar) after a large meal.
Low Energy and Cognitive Function: Dizziness, irritability, and lack of mental focus are commonly reported side effects of extended fasting.

OMAD vs. Traditional Meal Patterns: A Comparison

To better understand the trade-offs, here is a comparison between OMAD and a traditional, multiple-meal approach:


Feature	One Meal a Day (OMAD)	Multiple Meals per Day (e.g., 3-Hour Diet)
Caloric Control	Easier to create a deficit due to limited eating window, but also easier to over-consume due to intense hunger.	Consistent intake can prevent extreme hunger and potential bingeing, though portion control is key.
Nutrient Intake	High risk of nutritional deficiencies; very difficult to meet all requirements in one meal.	Allows for a more balanced and consistent intake of micronutrients and protein throughout the day.
Metabolic Impact	Can increase fat oxidation and improve insulin sensitivity, but may risk muscle loss.	Maintains a more stable metabolism without the metabolic stress of extreme fasting.
Satiety & Hunger	Experience intense hunger pangs for most of the day, with potential for binge eating.	Promotes more stable energy levels and reduces extreme hunger spikes.
Long-Term Sustainability	Often difficult to sustain for long periods due to strictness and potential side effects.	More flexible and sustainable for many people, promoting healthy, consistent eating habits.

Best Practices for Any Eating Pattern

If you are considering a restrictive eating plan like OMAD, or simply want to improve your nutrition, keep these points in mind:

Prioritize Nutrient Density: Focus on whole, unprocessed foods like fruits, vegetables, lean proteins, healthy fats, and whole grains.
Stay Hydrated: Drink plenty of water and other calorie-free beverages throughout the day, especially during fasting periods.
Listen to Your Body: Pay attention to hunger and fullness cues. If a particular eating pattern causes you excessive fatigue, irritation, or other negative side effects, it is not the right choice for you.
Consult a Professional: Always speak with a healthcare provider or a registered dietitian before starting any restrictive diet, especially if you have underlying health conditions like diabetes.

Conclusion: Focus on Calorie Balance, Not Just Meal Timing

The central question of whether you gain more weight by eating once a day is answered not by meal frequency but by a fundamental principle of nutrition: caloric balance. While the One Meal a Day (OMAD) diet can potentially aid weight loss by making it easier to maintain a calorie deficit, it is not a magical solution and comes with significant risks, including nutritional deficiencies, muscle loss, and blood sugar instability. Instead of focusing on extreme restrictions, a more sustainable and safer approach for most people involves eating a balanced, nutrient-dense diet and managing overall caloric intake. Ultimately, a healthy relationship with food and a sustainable lifestyle are far more important than adhering to a rigid, potentially risky, eating schedule. For additional scientific insights on meal frequency, consider reviewing the research available from institutions like the National Institutes of Health (NIH), which offer comprehensive studies on various dietary interventions.

Practical Tips for Healthy Eating, Regardless of Meal Frequency

Focus on Protein: Ensure sufficient protein intake to preserve muscle mass, which is crucial for a healthy metabolism.
Include Plenty of Fiber: Fiber from fruits, vegetables, and whole grains helps with satiety and supports digestive health.
Choose Healthy Fats: Incorporate healthy fats from sources like avocado, nuts, and olive oil to promote fullness and support bodily functions.
Don't Forget Micronutrients: With OMAD, it's particularly important to focus on nutrient-dense foods to compensate for the limited eating window.
Monitor Your Energy Levels: Pay close attention to how your body feels. If you experience fatigue, nausea, or dizziness, your diet may be the cause.

Frequently Asked Questions

For most people, eating multiple nutrient-dense meals throughout the day is a more balanced and sustainable approach for overall health. OMAD poses significant risks, including nutritional deficiencies and potential metabolic issues, and is not recommended as a long-term strategy for everyone.

Yes, it is possible to gain weight on OMAD if you consume more calories in your single meal than your body burns throughout the day. Weight gain is determined by your total caloric intake, not meal frequency.

While intermittent fasting can lead to shifts in metabolism, such as an increase in fat oxidation, long-term or extreme fasting can cause the metabolism to slow down. A slowed metabolism can make it harder to lose weight over time.

OMAD should be avoided by pregnant or breastfeeding women, children, teens, and people with a history of eating disorders. Individuals with underlying health conditions, such as diabetes or cardiovascular disease, should also avoid it or consult a doctor first, as it can cause dangerous blood sugar and cholesterol fluctuations.

OMAD can be effective for weight loss by naturally creating a caloric deficit. However, it is not necessarily more effective than other forms of calorie restriction and comes with greater risks of nutrient deficiencies and muscle loss.

Meeting all daily nutrient needs in one meal is very challenging. If you choose to follow OMAD, your single meal must be extremely nutrient-dense, packed with a wide variety of whole foods, including lean proteins, healthy fats, complex carbohydrates, and plenty of fruits and vegetables.

Yes, less restrictive forms of intermittent fasting, such as the 16:8 method, or simply adopting a balanced diet with regular meals are generally safer and more sustainable for long-term health and weight management.