OMAD Calculator
Calculate your optimal calories and macros for One Meal a Day eating
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Medical Disclaimer: This calculator provides estimates for educational purposes only and does not constitute medical advice. Intermittent fasting is not appropriate for everyone. Do not fast if you are pregnant or breastfeeding, under 18 years of age, have a history of eating disorders, or have been diagnosed with Type 1 diabetes. If you take medications (especially insulin or blood pressure medication), have any chronic health conditions, or are recovering from surgery, consult your physician before beginning any fasting protocol. If you experience chest pain, fainting, persistent dizziness, or heart palpitations during a fast, stop immediately and seek medical attention.
How to Use the OMAD Calculator
Enter your weight, height, age, sex, activity level, and goal (fat loss, maintenance, or muscle gain). The calculator determines your total daily energy expenditure and then calculates the optimal calorie target and macronutrient breakdown for a single meal. Because you are consuming an entire day of nutrition in one sitting, the macro split is adjusted to prioritize protein adequacy and nutrient density.
Choose your preferred eating time and the calculator will also suggest meal composition guidelines to help you hit your targets without digestive discomfort.
Understanding OMAD
OMAD, or One Meal A Day, is an intermittent fasting protocol with a roughly 23:1 fasting-to-eating ratio. You consume all of your daily calories within a single meal, typically lasting 30 to 60 minutes, and fast for the remaining 23 hours. This approach has gained popularity for its simplicity: there is no meal prep, no calorie counting throughout the day, and no decision fatigue around food.
Research on time-restricted eating suggests that condensing food intake into a shorter window can improve insulin sensitivity and promote fat oxidation. A 2023 study in Nature Medicine found that early time-restricted eating (eating earlier in the day) enhanced these metabolic benefits. However, OMAD is more extreme than typical time-restricted eating and is not appropriate for everyone, particularly those with high caloric needs, a history of disordered eating, or blood sugar regulation issues.
The primary challenge with OMAD is meeting your nutritional needs in one meal. Protein, fiber, vitamins, and minerals must all be consumed in a single sitting, which requires deliberate meal planning. This calculator helps you structure that meal to cover your requirements.
Key Takeaways
- OMAD works by creating a natural caloric deficit through extreme time restriction. Most people find it difficult to overeat in a single meal.
- Protein is the most critical macro to plan for on OMAD. Aim for at least 0.7 grams per pound of body weight to prevent muscle loss.
- Meal timing matters. Eating your single meal earlier in the day (lunch rather than late dinner) aligns better with circadian rhythms and may improve metabolic outcomes.
- OMAD is not recommended for athletes with high training volumes, as meeting caloric and glycogen replenishment needs in one meal is impractical.
- Digestive discomfort is common when starting OMAD. Begin with a 20:4 protocol and gradually narrow to 23:1 over 1 to 2 weeks.
Frequently Asked Questions
Can I build muscle on OMAD?
It is possible but significantly harder than with multiple meals. Muscle protein synthesis is optimized when protein is distributed across 3 to 4 feedings throughout the day. If muscle gain is your primary goal, a less restrictive protocol like 16:8 is more practical. If you do OMAD while training, prioritize a high-protein meal immediately after your workout.
What should I eat for my one meal?
Focus on protein first (chicken, fish, eggs, beef, tofu), then add complex carbohydrates (rice, potatoes, legumes), healthy fats (avocado, olive oil, nuts), and vegetables for fiber and micronutrients. Avoid filling up on low-calorie foods early in the meal, as you may not hit your calorie target.
Can I drink anything besides water during the 23-hour fast?
Black coffee, plain tea, sparkling water, and calorie-free electrolyte drinks are all acceptable during the fasting window. Avoid anything with calories, protein, or sweeteners that may trigger an insulin response.
Is OMAD safe long-term?
There is limited long-term human research specifically on OMAD. Short-term studies (up to 8 weeks) show it is generally safe for healthy adults. However, chronic undereating and nutrient deficiencies are risks if meals are not carefully planned. Many practitioners cycle between OMAD and less restrictive protocols to mitigate these concerns.
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