One Meal A Day (OMAD) is a dietary approach that restricts all caloric intake into a single, condensed eating window, typically lasting about one hour. For high-performance athletes, whose energy demands are significantly elevated, adopting this strategy is a specialized variation of intermittent fasting. This method requires a 23-hour daily fast, presenting a substantial physiological and logistical challenge for individuals who rely on consistent fuel for intense training and recovery. While OMAD offers potential simplicity, its application for high-volume training requires careful consideration of the body’s internal processes and nutrient requirements.
Metabolic Adjustments During Extended Fasting
When an athlete shifts to the OMAD pattern, the body must make significant internal adjustments to manage the prolonged period without energy intake. The primary change involves a metabolic shift from relying on circulating glucose to utilizing stored energy sources, a state often described as “metabolically flexible.” Initially, the body uses up glycogen stores in the liver and muscles. Once these reserves are depleted, the body begins to increase the oxidation of stored fat for fuel.
This prolonged fasting state leads to a lower and more stable insulin level, which can enhance insulin sensitivity in muscle cells. The low insulin environment facilitates the release of fatty acids from adipose tissue, which are then converted into ketones in the liver, providing an alternative fuel source. This process primes the athlete’s body to burn fat for energy, relevant for sustained, lower-intensity endurance activities. One study found that reducing meals to a single daily intake increased exercise fatty acid oxidation without negatively affecting aerobic capacity or muscular strength.
Strategic Nutrient Concentration in a Single Meal
The most significant practical challenge for an athlete on an OMAD schedule is consuming a day’s worth of high caloric and nutrient requirements in a single meal. Competitive athletes often require daily protein intakes ranging from 1.4 to 2.0 grams per kilogram of body weight to support muscle repair and growth. Concentrating this large amount of protein, carbohydrates, and fats into one sitting can be physically difficult and may challenge the digestive system.
To maximize nutrient density within the limited window, the meal must be meticulously planned using high-quality, whole food sources. Prioritizing lean protein, such as poultry, fish, or legumes, is necessary to meet the daily protein target, though the body’s capacity to utilize all of it for muscle protein synthesis in one bolus is debated. Adequate intake of complex carbohydrates is required to replenish muscle glycogen stores depleted during training. The meal must also be calorie-dense without being excessively voluminous to prevent gastrointestinal discomfort.
A single daily meal complicates the acquisition of sufficient micronutrients, including B vitamins, iron, and electrolytes, which are frequently depleted through intense training. Careful inclusion of a wide variety of fruits, vegetables, and healthy fats is necessary to ensure the athlete avoids deficiencies and supports recovery.
Performance and Muscle Maintenance Implications
For athletes, the timing of the single daily meal in relation to training is an important consideration for performance and recovery. The meal must be strategically scheduled to provide sufficient energy for the next training session and to optimize post-exercise recovery. Consuming the meal immediately following a workout is often preferred, as this timing allows for the rapid refueling of glycogen stores and provides the necessary amino acids to initiate muscle protein synthesis. Missing this post-exercise window can impair the body’s ability to recover and adapt to training.
The maintenance of muscle mass is a primary concern with OMAD, as consistent protein feeding throughout the day is considered superior for continually stimulating muscle protein synthesis. By having only one meal, an athlete misses multiple opportunities to elevate this synthesis rate, potentially hindering muscle growth or preservation. While some research suggests no detriment to aerobic capacity or strength, other studies have shown mixed results, including observed declines in muscle mass and performance. For strength and power athletes, the potential for reduced protein synthesis makes OMAD less ideal, while endurance athletes may find the enhanced fat oxidation beneficial for longer, lower-intensity efforts.