Relative Energy Deficiency in Sport (RED-S)

By Riley Nickols, PhD, CEDS

What is Relative Energy Deficiency in Sport (RED-S)?

In 2014, the International Olympic Committee (IOC) published the consensus statement Beyond the Female Athlete Triad: Relative Energy Deficiency in Sport whereby RED-S expanded upon the Female Athlete Triad’s three conditions: low bone mineral density, functional hypothalamic amenorrhea, and low energy availability (LEA).1,2 A primary tenet of RED-S is that any athlete, regardless of gender, sport, or competitive level can experience this syndrome.

It is important for athletes and sport personnel to understand how RED-S can have damaging effects on all systems in the body including psychological functioning. The RED-S framework includes more considerations due to low energy availability (LEA). LEA is a state in which the body does not have enough energy to support all of its functions. This leads to issues with reproductive health (menstrual dysfunction and low estrogen for females, low testosterone for males, decreased sex drive for those with LEA), cardiovascular function (unstable vital signs, bradycardia or tachycardia due to LEA), immune function, growth and development, hematological, gastrointestinal, and metabolic functioning. Psychological consequences can either precede RED-S or may worsen by RED-S.3,4

Despite the maintenance, or even improved, sport performance for a period of time, a continued state of RED-S will eventually negatively impact an athlete’s sport performance due to:1

  • Concentration and focus difficulties
  • Decreased training response
  • Increased injury risk
  • Decreased coordination and impaired judgment
  • Depression and irritability
  • Decreased glycogen stores
  • Decreased muscle strength and endurance performance

Although there is overlap between symptoms of RED-S and an eating disorder, there are differences between these two conditions. For this reason, qualified providers need to determine whether an eating disorder is also present in the context of a RED-S diagnosis.

What Causes of RED-S?

Low energy availability is the primary component of RED-S whereby there is a mismatch between an athlete’s nutritional/energy intake and the energy expended during exercise, so there is not enough energy to support the body’s functions to stay healthy and perform well.5

How to Detect RED-S

A specialist should evaluate if an athlete’s symptoms support a RED-S diagnosis. A comprehensive evaluation by a sports medicine physician should occur that entails obtaining an athlete’s medical history in addition to heart rate and blood pressure data to determine if an athlete meets criteria for RED-S and/or medical instability.6

Additionally, the multidisciplinary treatment team (i.e., sports medicine physician, sports dietitian, and mental health provider) should assess an athlete’s sport history, an athlete’s current training volume and intensity, eating behaviors, and be aware if any changes have recently occurred specific to an athlete’s mood, energy levels, fatigue, injury, hormonal functioning, and/or sport performance.6

Click here to access the IOC’s Relative Energy Deficiency in Sport (REDs) Clinical Assessment Tool Version 2 (IOC REDs CAT2) (NOTE: This assessment tool is intended for use by medical professionals only)

Treatment of RED-S

A Multi-Disciplinary Approach:

Treatment of disordered eating/eating disorders warrants a multidisciplinary team approach consisting of a physician, dietitian, and mental health provider who frequently collaborate on the care of an athlete.5


A physician should assess and monitor the physical health of an athlete with RED-S given the aforementioned systems of the body that can, and eventually will, be harmed as a result of prolonged LEA. A physician closely monitors the medical stability of an athlete with a RED-S diagnosis given the heart stress that LEA can cause. It is important for the physician to determine if specialists from other fields (e.g., endocrinology, gynecology, cardiology) are needed to best support an athlete with RED-S and to ensure such additional care by sub-specialists is coordinated and comprehensive.6


If an athlete’s LEA is the result of unintentional under-fueling, then nutrition education and additional professional support to restore energy is recommended for treatment.3 Nutrition and exercise changes should be made by a qualified provider (i.e., a board certified specialist in sports dietetics) to restore energy. If an athlete’s LEA is the result of intentional under-fueling, finding the reason behind the under-fueling is needed so that evidence-based sports nutrition education can be provided to the athlete. Additionally, if the athlete is intentionally under-fueling, further evaluation for an eating disorder is important.5

Mental Health Provider:

A mental health provider is necessary to help an athlete address the underlying reasons in the development and sustainment of RED-S. Support is often needed to address increased mood changes (i.e., depression, anxiety) that frequently occur, or intensify, as the result of RED-S and malnourishment. Athletes and mental health providers can work together on ways to best handle challenges that can arise from making necessary dietary and exercise changes to restore energy.5

Increased Nutrition:

Increased caloric intake via bigger portion sizes, eating more frequently, and/or incorporating more calorically dense foods into an athlete’s diet often comprise nutritional interventions to restore an athlete’s energy availability.5

Rest and Return to Sport Considerations: 

In addition to dietary modifications, stopping or decreasing the amount of training volume, training intensity, and/or sport participation are needed for energy restoration in a timely manner. In addition to using clinical judgment and collaboration from multidisciplinary treatment team members, the Safe Exercise at Every Stage Athlete Guideline and the IOC’s RED-S Clinical Assessment Tool (CAT) can also be used by providers to guide return to play decisions. Should an athlete be unable or unwilling to restore energy with appropriate nutrition and exercise interventions, then further evaluation is warranted by a qualified expert to determine if an eating disorder is present in conjunction with LEA.5

RED-S Preventative Measures

Increased education and awareness for athletes and sport personnel as to the negative effects of LEA are important protective factors to decrease the onset and sustainment of RED-S. Coaches, athletic trainers, and sport personnel should consult with qualified sports dietitians and physicians to assess an athlete’s individualized energy needs, determine the current state of energy availability of an athlete, and develop corresponding interventions to support positive energy availability.5

Importantly, safe and appropriate methods for monitoring an athlete’s body weight and shape should be developed within athletic organizations. Sport participation should be limited or withheld when certain weight and/or body composition are met. An additional protective measure for RED-S is the removal of toxic environments in sport where athletes are shamed for eating behaviors, shape and size of their bodies.5

Sport personnel can prioritize an athlete’s health by having enough water, sports drinks, and food available to athletes before, during, and after practices and competitions. Finally, it is important for coaches and trainers to consider having required team rest days and to address if/when an athlete is exceeding recommended training parameters. In addition to inadequate fueling to meet energy needs, training that is above an athlete’s training plan increases energy demands, making an athlete more likely to be in a state of energy deficiency.5


  1. Low bone mineral density: A condition that causes the amount of minerals contained in bones to decline, increasing risk of fractures
  2. Functional hypothalamic amenorrhea: A condition that causes the amount of minerals contained in bones to decline, increasing risk of fractures
  3. Low energy availability (LEA): A state in which the body does not have enough energy to support all of its functions
  4. Bradycardia: Slow heart rate
  5. Tachycardia: Fast heart rate
  6. Hematological: Relating to the blood
  7. Gastrointestinal: Relating to the stomach and the intestines
  8. Metabolic functioning: Relating to the chemical reactions in the body’s cells to produce energy.
  9. Glycogen stores: Glycogen stores serve as a form of energy storage for muscles.
  10. Unintentional under-fueling: Not consuming enough food for their activity level
  11. Energy demands: Use of energy by human activity
  12. Energy deficiency: The state in which there is not enough energy for body’s needs and for exercise


[1] Mountjoy, M., Sundgot-Borgen, J., Burke, L., Carter, S., Constantini, N., Lebrun, C., Meyer, N., Sherman, R., Steffen, K., Budgett, R., & Ljungqvist, A. (2014). The IOC consensus statement: beyond the Female Athlete Triad–Relative Energy Deficiency in Sport (RED-S). British journal of sports medicine, 48(7), 491–497.

[2] Otis, C. L., Drinkwater, B., Johnson, M., Loucks, A., & Wilmore, J. (1997). American College of Sports Medicine position stand. The Female Athlete Triad. Medicine and science in sports and exercise, 29(5), i–ix.

[3] Carson, T. L., West, B. T., Sonneville, K., Zernicke, R. F., Clarke, P., Harlow, S., & Karvonen-Gutierrez, C. (2023). Identifying latent classes of Relative Energy Deficiency in Sport (RED-S) consequences in a sample of collegiate female cross country runners. British journal of sports medicine, 57(3), 153–159.

[4] Loucks, A. B., Kiens, B., & Wright, H. H. (2011). Energy availability in athletes. Journal of sports sciences, 29 Suppl 1, S7–S15.

[5] Mountjoy, M., Sundgot-Borgen, J. K., Burke, L. M., Ackerman, K. E., Blauwet, C., Constantini, N., Lebrun, C., Lundy, B., Melin, A. K., Meyer, N. L., Sherman, R. T., Tenforde, A. S., Klungland Torstveit, M., & Budgett, R. (2018). IOC consensus statement on relative energy deficiency in sport (RED-S): 2018 update. British journal of sports medicine, 52(11), 687–697.

[6] Shanley, D., Hassan, A., Lunan, E., & Carmody, S. (2023). Relative energy deficiency in sport: Diagnosis and management in Primary Care. InnovAiT: Education and Inspiration for General Practice, 16(5), 229–235.

[7] Quesnel, D., Cooper, M., & Dobinson, A., (2019). Safe exercise at every stage: Athlete (SEES-A). A guideline for managing exercise and return to sport in athletes with eating disorders. Available at:

[8]  Mountjoy, M., Sundgot-Borgen, J., Burke, L., Carter, S., Constantini, N., Lebrun, C., Meyer, N., Sherman, R., Steffen, K., Budgett, R., Ljungqvist, A., & Ackerman, K. (2015). The IOC relative energy deficiency in sport clinical assessment tool (RED-S CAT). British journal of sports medicine, 49(21), 1354.