One Meal a Day (OMAD) is one of the most restrictive forms of intermittent fasting: you eat all of your daily food in a single meal and fast for the rest of the day. This page explains how OMAD works, how people usually build up to it, how to make one meal nutritionally complete, the possible benefits and downsides, who should not try it, and what the limited research shows.
Table of Contents
What is OMAD Fasting?
OMAD (One Meal a Day) is an intermittent fasting pattern in which you eat all of your daily food in a single meal, usually within about an hour, and fast for the remaining 23 hours or so. It is sometimes written as 23:1.
For example, you might eat dinner starting at 6 PM, finish by about 7 PM, and eat nothing else until 6 PM the next day.
Key Features of OMAD Fasting
- One-hour eating window per day
- 23 consecutive hours of fasting
- All daily nutrition concentrated in a single meal
- No calorie consumption during the fasting period (water, black coffee, and unsweetened tea permitted)
- Typically follows a consistent daily schedule
What sets OMAD apart from other daily fasting schedules is the long daily fast and the need to fit a whole day’s nutrition into one sitting. That makes it one of the more demanding approaches, and meeting nutritional needs is its main challenge.
Potential Benefits and Downsides
Most of the reported benefits of OMAD are practical and anecdotal; there is little direct research on it (see What Research Shows).
Calorie Control for Some People
Eating once a day makes it hard for some people to overeat, which can help create a calorie deficit. Others find the opposite: a single very large meal leads them to eat more than they need.
Simplified Meal Planning
Planning, preparing, and cleaning up after a single meal each day can save time and reduce daily decisions about food.
No Snacking Decisions
Some people like having a clear rule that removes snacking. Others find that long fasts make them think about food more, not less.
Food Appreciation
Some people say they enjoy their one meal more and eat it more mindfully.
Focus During the Day
Some people report feeling alert while fasting; others feel tired, irritable, or distracted by hunger. There is no good evidence that OMAD improves thinking or focus.
Possible Downsides
- It can be hard to get enough protein, fiber, vitamins, and minerals in a single meal
- Strong hunger before the meal, and overeating or feeling uncomfortably full after it
- Low energy, dizziness, headaches, or irritability, especially in the first weeks
- Social meals and family routines are harder to fit in
- In one small controlled trial of one meal a day, blood pressure and cholesterol rose slightly (see below)
- Higher risk of low blood sugar for people taking insulin or other glucose-lowering drugs
- For people prone to disordered eating, very restrictive schedules can trigger restrict/binge patterns
Important Note: Research specifically on OMAD is limited, and individual experiences vary widely. Talk to your healthcare provider before starting OMAD, especially if you have a medical condition or take medication.
How to Implement OMAD
Most people find a gradual transition easier than jumping straight to one meal a day. A typical approach:
Start With Less Intensive Fasting
If you're new to fasting, begin with a less restrictive protocol like 16:8 (16 hours fasting, 8 hours eating) and gradually extend your fasting window over several weeks or months.
Progress to Shorter Eating Windows
Incrementally reduce your eating window from 8 hours to 6 hours, then 4 hours, then 2 hours, allowing your body to adapt at each stage before proceeding to the next.
Choose Your Meal Time
Determine which meal of the day works best for your lifestyle, energy needs, and social circumstances. Common choices include dinner (for social flexibility) or lunch (for daytime energy).
Plan a Complete Meal
Make sure your one meal contains enough protein, healthy fats, carbohydrates, fiber, vitamins, and minerals to cover the whole day.
Maintain Consistent Timing
Try to eat at approximately the same time each day to establish a predictable rhythm for your body and digestive system.
Develop a Hydration Strategy
Drink water regularly during the fasting hours. Plain coffee, plain tea, and a little salt in water (if your healthcare provider has not advised limiting salt) help some people with headaches.
Nutritional Considerations
With OMAD, the quality and size of your meal matter more because you have only one chance each day to meet your nutritional needs.
Meeting Daily Requirements
Protein Priority
Protein supports muscle maintenance, and your one meal has to cover the whole day:
- Include a large portion of protein (fish, meat, eggs, dairy, tofu, tempeh, legumes)
- The general adult reference intake is about 0.8 g per kg of body weight per day; active people and older adults are often advised to aim higher
- Very large amounts at once can be hard to eat, which is one reason some people widen their eating window
Essential Fats
Include sources of unsaturated fats, which also help absorb fat-soluble vitamins:
- Omega-3 fats (oily fish, flaxseeds, walnuts)
- Monounsaturated fats (olive oil, avocados, nuts)
- Keep saturated fat moderate, in line with general dietary guidelines
Micronutrient Density
Focus on nutrient-rich foods to avoid deficiencies:
- Variety of colorful vegetables
- Fruit, whole grains, legumes, nuts, and seeds
- Dairy or fortified alternatives for calcium
- Ask your healthcare provider or a dietitian whether a supplement makes sense for you
Fiber & Prebiotics
Include adequate fiber for digestive health:
- Vegetables of different types
- Resistant starches (cooled potatoes, rice)
- Prebiotic fibers (Jerusalem artichokes, onions, garlic)
- Start gradually to avoid digestive discomfort
Important Consideration: Some individuals may find it challenging to consume adequate calories and nutrients in a single meal, particularly those with high energy requirements, athletes, or those trying to gain muscle mass. In such cases, a different fasting protocol might be more appropriate.
Meal Planning and Composition
A nutritionally complete OMAD meal takes some planning. Here is one way to structure it, with example meals.
OMAD Meal Structure
Some people like to eat their meal in courses. Eating vegetables and protein before starchy foods may modestly reduce the rise in blood glucose after the meal, though this is not essential:
Start with Vegetables
Begin with non-starchy vegetables, perhaps as a salad with olive oil dressing or a vegetable soup. It is a gentle way to start eating after a long fast.
Consume Protein Second
Follow with your main protein source.
Add Healthy Carbohydrates
Add whole grains, potatoes, legumes, or fruit to provide energy and fiber.
Include Healthy Fats Throughout
Include some fat (olive oil, avocado, nuts, fish) through the meal to help absorb fat-soluble vitamins.
Sample OMAD Meal Compositions
Omnivore OMAD Meal
Starter: Large mixed green salad with olive oil, vinegar, avocado, and various vegetables
Main: A generous portion of salmon, chicken, or lean beef with roasted vegetables
Sides: Baked sweet potato or whole-grain rice
Additional: Berries with yogurt and nuts
Note: A meal like this can easily reach 1,500-2,000 calories; adjust portions to your needs
Plant-Based OMAD Meal
Starter: Large salad with mixed greens, vegetables, and avocado with olive oil dressing
Main: Lentil and vegetable curry with coconut milk, served with quinoa
Sides: Roasted vegetables with herbs, tempeh with tahini sauce
Additional: Mixed nuts, seeds, and fresh fruit
Note: Combines several plant protein sources; vegans should also plan for vitamin B12, which plant foods do not reliably provide
Higher-Calorie OMAD (Active Individuals)
Starter: Vegetable soup and large salad with nuts and seeds
Main: A large protein portion with starchy vegetables
Sides: Rice or potatoes, additional vegetables with olive oil
Additional: Fruit, yogurt, nut butter, and perhaps a small dessert
Note: Very active people may need a very large meal to meet their needs, which many find difficult; a wider eating window is often more practical
Meal Timing Flexibility
While OMAD usually means about a one-hour eating window, some people extend it to 1-2 hours to eat more comfortably. For example, you might start with a salad, take a short break, then consume your main course, followed by another short break before dessert or additional food. This can make it easier to consume adequate calories and nutrients without discomfort.
Frequently Asked Questions
Can I exercise while following OMAD?
Many people do, but timing and intensity matter. Some prefer to train shortly before their meal so they can eat soon afterward. Light to moderate exercise is usually manageable during the fasting hours. Intense or long sessions are often harder without food, and very active people may find OMAD does not supply enough energy. See exercise timing and fasting.
Will OMAD slow my metabolism?
Any sustained calorie deficit and weight loss leads to some reduction in energy expenditure, whether it comes from OMAD or another diet. There is no clear evidence that OMAD slows metabolism more than other approaches with the same calorie intake. Eating enough overall, including enough protein, matters most.
How do I handle social situations on OMAD?
Social flexibility is one of the challenges of OMAD. Strategies include: 1) Schedule your one meal to coincide with social events when possible, 2) Consider occasional flexibility for special occasions, 3) Attend social gatherings but focus on the company rather than the food, or 4) Modify your approach to a wider eating window on specific days while maintaining the spirit of the protocol.
Is OMAD safe for everyone?
No. OMAD is not appropriate for people who are pregnant or breastfeeding, people with a current or past eating disorder, children and teenagers, people who are underweight, people with diabetes (especially those taking insulin or sulfonylureas) unless closely supervised, and people with certain other medical conditions or medications. Because it is so restrictive, even healthy adults should talk to a healthcare provider before starting.
What about coffee and other beverages during the fasting period?
Water, black coffee, plain tea, and other zero-calorie drinks are generally considered acceptable during the fast. Some people stick to water only, while others find caffeine takes the edge off hunger. Milk, cream, and sugar add calories and break the fast. The effects of zero-calorie sweeteners are debated; see diet soda and sweeteners.
How long does it take to adapt to OMAD?
It varies. Many people say the first few weeks are the hardest. Building up gradually from a wider eating window makes the transition easier. If OMAD still feels very difficult after several weeks, or you notice fatigue, poor sleep, or preoccupation with food, a less restrictive schedule is likely a better fit.
Tips for Success
Prioritize Nutrient Density
Focus on the most nutrient-rich foods during your meal, ensuring you get a spectrum of nutrients from diverse food sources.
Stay Hydrated
Drink water regularly through the fasting hours, and consider electrolytes if you are active or prone to headaches.
Implement Gradually
Allow your body time to adapt by progressively extending your fasting window over weeks or months rather than immediately jumping to OMAD.
Prepare Your Meal in Advance
Plan and prepare your nutritionally complete meal ahead of time to ensure you don't make compromised food choices due to excessive hunger.
Eat Mindfully
Take time to truly savor your one meal, eating slowly and paying attention to hunger and satiety cues rather than rushing through it.
Monitor Non-Scale Indicators
Pay attention to energy levels, sleep quality, mood, and other indicators of wellbeing rather than focusing exclusively on weight-related outcomes.
Common Challenges and Solutions
Extreme Hunger
Challenge: Experiencing intense hunger, especially in the hours before your meal.
Solutions:
- Stay well-hydrated throughout the day
- Black coffee or plain tea can take the edge off hunger for some people
- Schedule engaging activities during peak hunger periods
- Consider adjusting your meal timing to better align with your natural hunger patterns
- If hunger is overwhelming, switch to a less restrictive schedule such as 16:8 or 18:6
Digestive Discomfort
Challenge: Experiencing bloating, discomfort, or digestive issues after consuming a large meal.
Solutions:
- Consider extending your eating window slightly (up to 2 hours) for more relaxed consumption
- Start your meal with easily digestible foods
- Chew thoroughly and eat mindfully
- Avoid very greasy or very large portions at the start of the meal
- If discomfort continues, a wider eating window or two meals may suit you better
Difficult Social Situations
Challenge: Navigating social meals, work lunches, or family dinners outside your eating window.
Solutions:
- Consider scheduling flexibility for important social occasions
- Shift your eating window when necessary for special events
- Focus on the social aspect rather than the food
- Be transparent with close friends and family about your eating pattern
- Plan your social calendar around your eating window when possible
Getting Adequate Nutrition
Challenge: Consuming sufficient calories, protein, and micronutrients in a single meal.
Solutions:
- Plan meals around vegetables, protein, whole grains or potatoes, fruit, and healthy fats
- Consider calorie-dense but nutritious foods (nuts, avocados, olive oil)
- Use a nutrient tracking app occasionally to assess your intake
- Ask a healthcare provider or dietitian whether you need a supplement
- If consistently struggling, consider a slightly wider eating window
What Research Shows
Research on intermittent fasting has grown, but very few studies have tested eating one meal a day. Here is what the available evidence suggests:
Single Daily Meal Timing Studies
A small controlled trial compared eating one meal a day in the evening with eating three meals a day, with the same total calories, in healthy normal-weight adults over several weeks. On one meal a day, participants lost a small amount of body fat, but they also reported more hunger, and their blood pressure and cholesterol rose slightly. It was short and small, so the results should be interpreted with caution.
A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. American Journal of Clinical Nutrition (2007).
Time-Restricted Eating Studies
Studies of shorter daily eating windows are more common. One small, well-controlled study in men with prediabetes found that eating within a 6-hour window ending in the mid-afternoon improved insulin sensitivity and blood pressure over five weeks compared with a 12-hour window. This was not OMAD: participants ate three meals in an early window. It suggests meal timing may matter, but it cannot be assumed to apply to a single evening meal.
Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metabolism (2018).
Hunger and Adaptation Patterns
Hunger is partly shaped by habitual meal times, which is why it often comes in waves around your usual meals. Many people report that hunger becomes easier to manage after a few weeks on a new schedule, but the evidence is mixed: some fasting studies have found that hunger on fasting days stays high rather than fading.
Important Note: Research specific to OMAD is limited, and its long-term benefits and risks have not been well studied. This information is for education only and is not medical advice. Talk to your healthcare provider before starting a restrictive fasting schedule.
The Bottom Line
OMAD means eating all of your daily food in one meal and fasting for about 23 hours. Its main appeal is simplicity; its main challenges are hunger, social meals, and getting enough nutrition in a single sitting. Direct research is limited, and one small trial found slight rises in blood pressure and cholesterol.
If you want to try it, build up gradually from a wider eating window, plan a complete meal, and stop or switch to a less restrictive schedule if you feel unwell. It is not suitable for everyone, so check with your healthcare provider first.
Track Your Fasting Hours
Our free browser-based fasting timer can help you keep track of your fasting and eating windows.