Are Humans Supposed to Eat Once a Day?

December 7, 2025 •

4 min read

Historically, the modern three-meals-a-day structure is a relatively recent development, largely shaped by the Industrial Revolution. However, the question remains: are humans supposed to eat once a day, a practice known as the One Meal a Day (OMAD) diet?. This extreme form of intermittent fasting has garnered attention, but its long-term health implications are still under scrutiny by medical professionals.

Quick Summary

The OMAD diet involves consuming all daily calories within a short, typically one-hour, window. While some studies suggest benefits like weight and fat mass reduction, this restrictive eating pattern presents significant risks, including nutritional deficiencies, blood sugar fluctuations, and potential impacts on cardiovascular health. Sustainability issues and the risk of disordered eating are also major concerns. It's an extreme approach not recommended for most people without medical supervision.

Key Points

OMAD is not a natural human pattern: The three-meals-a-day structure is a modern construct, but eating one meal a day is an extreme, not naturally occurring, practice for humans.
Risks often outweigh benefits: The significant risks of nutritional deficiencies, blood sugar instability, and cardiovascular issues typically outweigh the anecdotal benefits of weight loss and simplified eating for most people.
Not recommended for everyone: Individuals who are pregnant or breastfeeding, children and teens, older adults, and those with a history of disordered eating or diabetes should avoid the OMAD diet.
Sustainability is a major issue: Most experts agree that OMAD is difficult to sustain long-term and often leads to high dropout rates and potential weight regain.
Less extreme fasting is often better: Health experts frequently recommend less restrictive forms of intermittent fasting, like the 16:8 method, which offer similar health benefits with fewer risks.
Nutrient-dense food is key: Regardless of meal frequency, prioritizing a balanced, nutrient-dense meal is crucial for health and to minimize potential risks if attempting OMAD under medical supervision.

The Evolutionary Perspective on Meal Frequency

Contrary to the common belief that humans have always eaten multiple meals a day, our eating patterns have evolved considerably over time. For millennia, our hunter-gatherer ancestors faced periods of food scarcity, meaning meals were irregular and feast-or-famine cycles were the norm. This may have physiologically habituated the human body to less frequent meals and promoted metabolic flexibility, the ability to switch between carbohydrate and fat oxidation for energy. However, this is a far cry from the modern, intentional practice of a One Meal a Day (OMAD) diet. Today's OMAD followers operate in an environment of food abundance, which presents a very different metabolic and nutritional landscape than that of our ancestors.

The Science Behind the OMAD Diet

The OMAD diet is an extreme form of intermittent fasting, restricting all daily calorie intake to a 1–2 hour window. The 22–23 hour fasting period triggers several metabolic changes. When the body runs out of its primary fuel source, glucose, it begins to burn stored fat for energy, a state known as ketosis. This metabolic shift can lead to weight and fat loss, as seen in some small, short-term studies. However, the extreme nature of OMAD differs significantly from other, more moderate, time-restricted eating methods, and research on its long-term effects is limited.

Potential Benefits and Noteworthy Risks

While some individuals report positive experiences with OMAD, the risks must be weighed carefully against the touted benefits. For example, some may experience initial weight loss due to significant calorie restriction, while others may find the diet unsustainable.

Benefits of OMAD

Simplified eating: Advocates praise the simplicity of only preparing and consuming one meal daily, which saves time and reduces mental energy spent on food decisions.
Potential metabolic shifts: Fasting periods may promote metabolic switching and cellular repair processes like autophagy.
Cognitive effects: Some anecdotal reports and studies on intermittent fasting suggest potential improvements in cognitive function, including enhanced focus and mental clarity.

Risks of OMAD

Nutritional deficiencies: Consuming all required nutrients in a single meal is extremely difficult, risking deficiencies in essential vitamins and minerals.
Blood sugar instability: Individuals on OMAD may experience severe blood sugar fluctuations, which can lead to fatigue, irritability, dizziness, and is particularly dangerous for people with diabetes.
Disordered eating patterns: The restrictive nature of OMAD can foster an unhealthy relationship with food and may trigger or exacerbate disordered eating behaviors like binge eating.
Cardiovascular issues: Some studies have observed an increase in LDL cholesterol and blood pressure in people on OMAD, raising concerns about long-term cardiovascular health.

OMAD vs. Other Meal Patterns: A Comparison

To understand if one meal a day is right for you, it helps to compare it to more traditional eating patterns.


Feature	OMAD (One Meal a Day)	Traditional (3+ Meals a Day)	Time-Restricted Eating (e.g., 16:8)
Sustainability	Low for most people; high dropout rates.	High; aligns with modern societal schedules.	Moderate to High; less restrictive than OMAD.
Weight Management	Can cause rapid initial weight loss, but often involves significant muscle loss alongside fat loss. Not superior to traditional calorie restriction in long-term studies.	Sustainable for long-term weight management when calories are controlled.	Can be effective for weight loss without the extremes of OMAD.
Nutritional Intake	Very difficult to achieve balanced nutrient intake in one large sitting.	Easier to distribute nutrient-dense foods throughout the day.	Allows for multiple balanced meals within the eating window.
Blood Sugar Control	Associated with increased fasting glucose levels and poorer insulin response in some studies.	Often better for regulating blood sugar levels and avoiding spikes and crashes.	Generally improves insulin sensitivity and blood sugar control.
Impact on Energy	Can cause fatigue, low energy, and difficulty concentrating due to prolonged fasting.	Helps maintain stable energy levels throughout the day.	Many report stable energy and mental clarity during fasting periods.

Practical Considerations for the One-Meal-a-Day Approach

Given the risks, experts generally advise against the OMAD diet as a long-term strategy for weight loss or health improvement, especially given the lack of sufficient long-term research. Those considering any extreme dietary changes should always consult a healthcare provider, particularly if they have pre-existing conditions like diabetes or a history of disordered eating.

For those still interested in exploring meal frequency changes, less restrictive forms of intermittent fasting, such as the 16:8 method, are often recommended as a safer and more sustainable alternative. These methods offer many of the same potential benefits of fasting without the extreme risks associated with cramming all nutritional needs into one meal. Instead of focusing on the timing of a single meal, a healthier and more sustainable approach involves prioritizing a balanced diet rich in whole, nutrient-dense foods, combined with regular physical activity.

Conclusion

While a single-meal-a-day eating pattern is an intriguing area of nutritional science, the evidence suggests it is not a physiologically necessary or broadly recommended approach for humans. The practice is an extreme form of fasting with limited long-term research, and the potential for nutritional deficiencies and metabolic complications is significant. Unlike our ancestors who adapted to periods of scarcity, modern individuals can achieve health benefits, including weight management and improved metabolic markers, through less restrictive and more sustainable methods of eating. Ultimately, listening to one's body, focusing on a high-quality diet, and consulting medical professionals are far more important for long-term health than adhering to a rigid, one-meal structure. A sustainable approach to health prioritizes balance and nourishment over extreme restriction.

Reference source: Healthline.com, Medical News Today.

Frequently Asked Questions

The One Meal a Day (OMAD) diet is an extreme version of intermittent fasting where you consume all of your daily calories within a single 1-2 hour eating window, fasting for the remaining 22-23 hours.

Yes, it is possible to lose weight on the OMAD diet due to the significant calorie restriction it imposes. However, studies show it is not necessarily more effective for long-term weight loss than traditional calorie-controlled diets and may cause muscle mass loss.

When you eat once a day, your body enters a prolonged fasting state, shifting from burning glucose to burning stored fat for energy. This can lead to potential weight loss but also comes with side effects like fatigue, irritability, and nutrient deficiencies.

No, eating one meal a day is generally not recommended for people with diabetes. The practice can cause dangerous fluctuations in blood sugar levels and increase the risk of hypoglycemia.

For most people, the OMAD diet is not considered a sustainable long-term eating strategy due to its restrictive nature, potential for side effects, and risk of rebound weight gain.

The biggest risks include developing nutritional deficiencies, experiencing blood sugar and blood pressure issues, suffering from fatigue, and potentially fostering a disordered relationship with food.

Safer and more sustainable alternatives to the OMAD diet include less restrictive intermittent fasting methods, such as the 16:8 or 5:2 plans, which provide many of the same benefits with fewer risks.