One meal a day has not been shown to extend or shorten a runner's life. The clearer risk is underfueling: repeatedly leaving too little energy for training, recovery, and normal body functions. The only cited randomized OMAD trial followed 11 healthy, lean adults for 11 days—not runners or long-term health outcomes—so it cannot answer the longevity question, according to the 2022 Frontiers in Physiology study. Runners should judge OMAD by whether it supports adequate energy and nutrients, not by meal timing alone.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What is low energy availability?
- Why sustained underfueling matters
- Performance can decline quickly
- What the evidence says about long-term durability
- How to decide whether OMAD fits your running
What is low energy availability?
Low energy availability, or LEA, occurs when food intake minus exercise expenditure leaves insufficient energy for normal body functions. It can happen unintentionally and does not necessarily indicate an eating disorder. A runner may consume what seems like a substantial dinner yet still fall short after a long run or demanding training block.
Compressing all food into one meal can make the mismatch harder to recognize. Energy availability is often expressed as calories available per kilogram of fat-free mass each day. That calculation is mainly a clinical or research tool; runners do not need to track it precisely to take persistent underfueling seriously.
Why sustained underfueling matters
The International Olympic Committee identifies prolonged or severe problematic LEA as the cause of relative energy deficiency in sport, or REDs. REDs affects men and women and can impair reproductive, musculoskeletal, immune, cardiovascular, hematological, glycogen-synthesis, and other functions, as detailed in the 2023 IOC consensus statement. These effects connect daily fueling with both running durability and broader health.
Poor glycogen restoration can undermine training, while impaired bone or blood-related function may increase the chance that an athlete cannot train consistently. This does not prove that OMAD itself causes REDs. A one-meal schedule becomes concerning when it repeatedly fails to cover the runner's energy and nutrient needs relative to exercise.
Performance can decline quickly
Short controlled studies show that LEA can affect trained runners and endurance athletes within days or weeks. In 12 endurance-trained women, 14 days at an average of 22.3 rather than 51.9 kcal/kg fat-free mass/day reduced 20-minute time-trial performance by 7.8%. The deficit remained after three days of refueling, according to the 2024 FASEB Journal experiment.
A three-day study of six male long-distance runners compared energy availability of 20 and 45 kcal/kg fat-free mass/day during daily 75-minute runs. The lower-energy condition reduced muscle glycogen and increased next-day hepcidin, a regulator of iron availability. Another 14-day experiment in 12 trained male endurance athletes found lower hemoglobin, reduced explosive power, altered lactate metabolism, and worse reported well-being during LEA. These studies were small and brief, but they challenge the idea that an athlete can always compensate for inadequate intake through discipline or adaptation.
What the evidence says about long-term durability
No cited study directly tests whether OMAD changes lifespan, healthspan, or running longevity. Available evidence instead identifies plausible threats to sustained participation, including impaired recovery, reduced performance, and injury-related problems. In a cross-sectional study of national- and world-class distance athletes, amenorrheic women and men with low testosterone had lower relevant hormone levels.
Bone injuries were about 4.5 times more prevalent in those groups, according to the 2018 International Journal of Sport Nutrition and Exercise Metabolism study. Because that study observed athletes at one point in time, it cannot prove that LEA caused the injuries. Still, the association matters for runners whose goal is to remain healthy enough to train over many years.
How to decide whether OMAD fits your running
Do not treat the eating window as the main safety test. Consider whether the pattern consistently supports your total intake, training demands, recovery, and normal physiological function.
A practical review should ask: If REDs is suspected, the IOC recommends clinical assessment that considers other possible diagnoses. Management centers on restoring optimal energy availability by changing food intake, exercise demands, or both. A qualified clinician or sports dietitian can assess the full situation rather than attributing every problem to meal timing.
- Can one meal realistically replace the energy spent during regular training?
- Does the schedule permit adequate fueling around longer or harder runs?
- Has performance, recovery, well-being, or training consistency worsened?
- Are hormone, bone, blood, immune, or cardiovascular concerns emerging?
- Does the pattern become less workable when mileage or intensity rises?
