What Will Happen if You Eat Every 24 Hours?

January 12, 2026 •

3 min read

Restricting calorie intake to one meal a day, a form of intermittent fasting known as OMAD, triggers significant hormonal and metabolic changes. Proponents suggest it can simplify weight loss and boost metabolic health, but experts caution about potential risks and sustainability issues. Understanding what will happen if you eat every 24 hours is crucial for determining if this extreme eating pattern is right for you.

Quick Summary

This article explores the physiological effects of eating one meal every 24 hours (OMAD), including metabolic shifts, potential weight loss, and cellular repair processes. It also addresses significant health concerns, such as nutrient deficiencies, blood sugar imbalances, and the impact on energy levels. The sustainability and safety of this diet are discussed, emphasizing the importance of expert consultation.

Key Points

Metabolic Switch: After about 8-12 hours of not eating, the body shifts from burning glucose to burning stored fat for energy.
Insulin Sensitivity: Fasting for prolonged periods can lower insulin levels, potentially improving insulin sensitivity and aiding blood sugar control.
Autophagy and Repair: Extended fasting triggers cellular repair processes, including autophagy, which removes waste and recycles dysfunctional components.
Risks of Deficiency: It is very difficult to obtain all necessary nutrients from a single meal, leading to potential deficiencies, fatigue, and other health issues.
Cardiovascular Health: Some research has found that OMAD may increase total and LDL cholesterol and blood pressure levels.
Hormonal Changes: Prolonged fasting can increase the hunger hormone ghrelin and disrupt other hormones, potentially leading to binge eating.
Expert Caution: Most healthcare professionals do not recommend OMAD as a safe, long-term dietary strategy, especially for certain populations.

The Metabolic Shift: What Happens During Extended Fasting

When you eat every 24 hours, your body undergoes a metabolic change known as a “metabolic switch”. Initially, your body uses stored glucose for energy. After about 8-12 hours, as glucose stores deplete, it begins burning fat for fuel, entering a state called ketosis. This prolonged fasting lowers insulin levels, promoting fat burning and potentially improving insulin sensitivity. The body also activates cellular repair processes, like autophagy, which clears out damaged cells.

Potential Benefits of Eating One Meal a Day (OMAD)

Eating one meal a day can offer some advantages. It may simplify daily life by reducing meal planning time. Many individuals experience fat loss and improved blood sugar control. One study noted that eating a single evening meal resulted in greater reductions in body weight and fat mass compared to three meals, even with the same total calories. Some people also report improved mental clarity, which they attribute to stable blood sugar and ketone production. The extended digestive rest may also aid gut health.

The Risks and Downsides to a 24-Hour Eating Pattern

Despite potential benefits, health experts highlight significant risks with OMAD. A major concern is the difficulty of consuming all necessary vitamins, minerals, fiber, and protein in one meal, potentially leading to deficiencies, fatigue, weakened immunity, and bone density loss. Studies also suggest this restrictive pattern might increase total and LDL cholesterol and blood pressure.

Potential Side Effects of OMAD Include:

Fatigue and low energy: Inconsistent energy supply can cause lethargy, dizziness, and concentration issues during fasting periods.
Extreme hunger and cravings: Prolonged fasting can raise ghrelin, the hunger hormone, potentially leading to overeating unhealthy foods during the eating window.
Impact on mood: Fluctuating blood sugar and extended hunger can cause irritability and mood swings.
Social isolation: This diet can make social events centered around meals difficult.
Muscle loss: The body might break down muscle for energy during long fasts, impacting strength and metabolism.

OMAD vs. Other Intermittent Fasting Methods

OMAD is a strict form of intermittent fasting (IF) with a 23-hour fast. Less extreme methods, such as the 16:8 method (16 hours fasting, 8 hours eating), are often more sustainable and better researched. A 2022 study found similar weight loss between time-restricted eating (8 am-4 pm) and daily calorie restriction, suggesting the benefit is more about calorie reduction than the extreme eating window.

OMAD vs. Less Restrictive Fasting Table


Feature	One Meal a Day (OMAD)	16:8 Intermittent Fasting
Eating Window	1-2 hours	8 hours
Fasting Period	22-23 hours	16 hours
Sustainability	Low for most people; very restrictive	Higher; more flexible with social life
Nutrient Intake	High risk of nutrient deficiencies; hard to meet needs	Easier to meet daily nutritional requirements
Energy Levels	Significant fluctuations, potential for fatigue and dizziness	More stable energy; less risk of blood sugar crashes
Calorie Intake	Can lead to automatic calorie reduction, but also risks overeating	More balanced calorie distribution throughout the window
Evidence	Limited long-term human studies; many risks highlighted	More evidence supporting benefits with fewer adverse effects

The Role of Timing and Food Quality

The timing of the single meal may influence outcomes; eating earlier might improve glucose control, while a large late meal could worsen glucose tolerance. Crucially, the nutritional quality of the single meal is vital. A meal lacking essential nutrients or composed of processed foods can negate potential fasting benefits and lead to long-term health problems. Prioritize a meal rich in whole foods, lean protein, and healthy fats if attempting OMAD.

Conclusion

Eating every 24 hours (OMAD) is an extreme intermittent fasting method with varied effects. While it may lead to weight loss, improved insulin sensitivity, and cellular repair for some, it poses significant risks. Potential nutrient deficiencies, muscle loss, hormonal issues, fatigue, and mood swings are concerns. Most healthcare professionals advise against long-term, strict OMAD and recommend more balanced patterns. It can be particularly risky for those with conditions like diabetes. Consulting a healthcare professional is crucial before starting such a restrictive diet.

Link to Further Reading

Frequently Asked Questions

For most healthy adults, occasional OMAD is likely safe, but doing it long-term can be dangerous and is not recommended by most health experts. Potential risks include nutrient deficiencies, hormonal imbalances, and negative impacts on cardiovascular health.

Yes, many people do lose weight on an OMAD diet because it naturally restricts overall calorie intake. However, it is not necessarily more effective for long-term weight loss than other, more sustainable methods like regular calorie restriction.

While short-term fasting does not significantly slow metabolism, prolonged or extreme fasting, such as with a poor-quality OMAD diet, can cause the body to enter a 'starvation mode' that slows the metabolic rate.

The OMAD diet is not suitable for everyone, including children, teenagers, older adults, pregnant or breastfeeding women, and those with a history of eating disorders or medical conditions like diabetes.

OMAD is a more extreme and restrictive form of intermittent fasting than methods like the 16:8 schedule. While it may offer benefits, it also carries higher risks and is less sustainable for most people.

If you follow an OMAD diet, your one meal should be rich in nutrients and include a balanced mix of proteins, healthy fats, complex carbohydrates, and plenty of fruits and vegetables to counter the risk of nutritional deficiencies.

Yes, eating one meal a day can cause significant fluctuations in blood sugar, which can lead to irritability, mood swings, and difficulty concentrating due to a lack of consistent energy supply.