The OMAD diet, short for “One Meal a Day,” is an extreme form of intermittent fasting in which someone fasts for around 23 hours and consumes all of their daily calories in a single eating window typically one hour. Proponents say it simplifies eating habits, reduces decision fatigue around meals, and can lead to weight loss by creating a significant calorie deficit. However, the scientific research specific to this regimen is limited, and experts emphasize that its effects both positive and negative are tied closely to what and how much you eat during that one meal.
How OMAD Works
Like other intermittent fasting methods, the OMAD diet is based on the idea that long periods without eating force the body to shift how it uses energy. After several hours without food, insulin levels drop and the body begins burning stored fat for fuel, a process that may support weight loss. Many people on OMAD drink non-caloric beverages such as water, black coffee, or unsweetened tea during the fasting period to help manage hunger. Despite this mechanism, experts point out that weight loss on OMAD typically happens because people naturally eat fewer calories overall, not because the fasting period itself has unique metabolic effects. In fact, research comparing intermittent fasting approaches with traditional calorie restriction finds similar weight loss outcomes, suggesting that simply reducing daily calories even with a regular meal pattern can be just as effective.
Potential Benefits
Weight Loss
Many people are drawn to OMAD because it can produce a calorie deficit, leading to fat loss for those who consume fewer calories than they expend. Studies on intermittent fasting with extended fasting windows show that restricting eating times can help reduce body fat and total body weight, even without specific calorie counting.
Simplified Eating
Some followers report that eating just once a day simplifies their meal planning and may reduce cravings, potentially helping them stick to healthier food choices within the limited time frame.
Metabolic Effects
Research on less extreme forms of time-restricted eating suggests potential benefits like improved insulin sensitivity, blood sugar regulation, and lower triglycerides, although these effects are not yet conclusively demonstrated for strict OMAD.
Risks and Safety Concerns
Nutrient Deficiencies
One of the biggest concerns with eating only once per day is that it may be difficult to meet daily requirements for essential nutrients such as vitamins, minerals, protein, and fiber. This is especially challenging if the single meal isn’t carefully planned to include a wide variety of nutrient-dense foods.
Blood Sugar and Metabolic Issues
Eating a large amount of food in one sitting after a long fast may cause blood sugar spikes, followed by drops during the fasting period. This pattern can be particularly risky for people with diabetes or those prone to hypoglycemia. Some research also links extended fasting with higher fasting glucose levels compared with normal meal patterns.
Cardiovascular Concerns
Some older studies indicate that extreme fasting diets like OMAD may be associated with increased cholesterol and blood pressure in certain individuals, potentially raising cardiovascular risk over time.
Hunger, Energy, and Sustainability
Strict fasting often leads to intense hunger, fatigue, irritability, and difficulty concentrating, especially in the early stages. Many people find it hard to sustain OMAD long-term, and the diet can interfere with social meal patterns and everyday activities.
Who Should Avoid OMAD
Health experts generally advise that the OMAD diet is not suitable for everyone. Groups who should avoid this pattern — or consult a healthcare provider before trying it — include:
People with diabetes or metabolic disorders
- Individuals taking medications requiring food with doses
- People with a history of eating disorders
- Pregnant or breastfeeding women
- Children, teens, and older adults
Bottom Line
While the OMAD diet may help some people lose weight and simplify their eating patterns, research specific to eating only one meal a day is limited. Evidence suggests that intermittent fasting styles can offer benefits, but these are not unique to OMAD and may come with significant risks and downsides — especially if the meal lacks nutritional balance or the fasting period is poorly managed. Most health professionals recommend more moderate approaches to intermittent fasting or traditional balanced diets tailored to individual needs and long-term sustainability.
