Relative Energy Deficiency in Sport (Red-S)

April 15, 2019

What is RED-S?

Relative Energy Deficiency in Sport (RED-S) is a syndrome that refers to impaired physiological function and the consequences caused by relative energy deficiency, which can include disturbances in metabolic rate, menstrual function, bone health, immunity, protein synthesis, and cardiovascular health.  The underlying cause of RED-S is low energy availability (LEA).  LEA occurs when an athlete is expending more energy through exercise and activities of daily living than they are taking in through diet and nutrition (5).  From an evolutionary perspective, LEA due to periods of food scarcity or extreme energy expenditure causes the body to make adaptations in order to sustain life (3).  The human body makes such adaptations by diverting its energy away from processes that are not needed for immediate survival, such as growth, development, and fat accumulation (3).  In doing so, the body’s hormonal secretion is significantly altered from what is typical in order to maximize efficacy in a state of low energy.  This mechanism is beneficial for general survival, but it is not beneficial for optimal health or athletic performance.


Risk Factors

While most of the scientific literature studies the female athlete population, active males can also be at risk for developing RED-S.  The frequency, duration, and magnitude in which one’s body is in a state of LEA can vary between populations depending on sport, gender, and diagnosis.  Common risk factors for both males and females includes frequent fluctuation in body weight/mass, the high energy cost of training, food insecurity, a high degree of competitiveness, and a high pain tolerance (1).  These risk factors can be more prominent in athletic populations who play sports that emphasize a lean appearance, such as in swimming, gymnastics, combat sports, or jockeying.

Disordered eating behavior may be more prevalent among athletic populations at risk for RED-S.  Weight pressure that comes with this unique type of disordered eating risk has reported trigger factors that include, but are not limited to: performance pressure, sudden increase in training volume, injury, teammate modeling of disordered eating behavior, team weigh-ins, a desire to be leaner to enhance performance, a dysfunctional coach-athlete relationship, and perfectionism.  It is essential that coaches, trainers, and health professionals working with these susceptible athletic populations understand risk factors and engage athletes in the appropriate screening (5).



Current evidence suggests that less than 50% of physicians, coaches, physiotherapists and athletic trainers are unable to identify negative health components associated with LEA (5).  Symptoms are typically subtle, underestimated, or undiagnosed, while the health ramifications can be significant. Professionals should understand that early detection of athletes at risk for RED-S is critical to prevent long-term health consequences, and if risk factors are identified in an athlete, that athlete should be referred to the appropriate healthcare providers. Additionally, professionals working with these athletes should create an environment that ensures and encourages athletes to engage in eating behaviors to optimize performance, and minimizes the focus on body weight measurement as a performance marker (7).  However, sometimes a change in body composition is needed for athletes to improve performance outcomes; If this is the case, a multidisciplinary team should be required to help an athlete safely manipulate their body composition, and prevent both short and long-term health consequences of LEA (6).  Professional education is ultimately needed to protect athletes from the health and performance outcomes associated with LEA (6).


Nutritional Considerations

While a medical diagnosis is required for RED-S, the condition can be treated through nutritional intervention that helps an athlete achieve an energy intake that better balances how much energy the athlete burns.  Treatment is typically based on increased food intake (5), and failure to adequately satisfy an increased nutritional requirement through food could result in increased injury risk, greater incidence of muscle soreness, decreased ability for muscle to recover after exercise, decreased immune function, subsequent increased risk of illness, and less overall power and endurance (7).  Athletes should consume adequate energy, carbohydrate, protein, and fat appropriate for their sport.  Micronutrient deficiencies should be addressed, particularly those related to bone growth which includes iron, calcium, and vitamin D.  Nutritional outcomes can be analyzed through changes in an athlete’s body composition, but these results must be explained using appropriate language that emphasizes lean mass and does not emphasize body fat (7).



RED-S is a serious health condition that often goes unnoticed until an individual has been suffering from the consequences associated with LEA for some period of time.  Health and performance outcomes of athletes can be significantly improved if sports medicine professionals understand how identify risk factors, and refer athletes to the appropriate healthcare providers to complete screening, diagnosis, and treatment.

Need a nutrition consult in the Houston area? Schedule an appointment with one of our dietitians at Memorial Hermann IRONMAN Sports Medicine Institute by phone 713-897-7912 or email ( Follow us on Facebook!



  1. Burke, L. M., Close, G. L., Lundy, B., Mooses, M., Morton, J. P., & Tenforde, A. S. (2018). Relative energy deficiency in sport in male athletes: A commentary on its presentation among selected groups of male athletes. International Journal of Sports Nutrition and Exercise Metabolism, 1-11.
  2. Carter, S. (2018). Female athlete triad/relative energy deficiency in sport: A perspective interview with professor barbara drinkwater. International Journal of Sports Nutrition and Exercise Metabolism, 28, 332-334.
  3. Elliott-Sale, K. J., Tenforde, A. S., Parziale, A. L., Holtzman, B., & Ackerman, K. E. (2018). Endocrine effects of relative energy deficiency in sport. International Journal of Sport Nutrition and Exercise Metabolism, 28, 335-349.
  4. Melin, A., Tornberg, A. B., Skouby, S., Faber, J., Ritz, C., Sjodin, A., & Sundgot-Borgen, J. (2014). The LEAF questionnaire: A screening tool for the identification of female athletes at risk for the female athlete triad. British Journal of Sports Medicine, 48, 540-545.
  5. Mountjoy, M., Sundgot-Borgen, J., Burke, L., Ackerman, K. E., Blauwet, C., Constantini, N., . . . Budgett, R. (2018). International olympic committee (IOC) consensus statement on relative energy deficiency in sport (RED-S): 2018 update. International Journal of Sport Nutrition and Exercise Metabolism, 28, 316-331.
  6. Mountjoy, M. L., Burke, L. M., Stellingwerff, T., & Sundgot-Borgen, J. (2018). Relative energy deficiency in sport: The tip of an iceberg. International Journal of Sport Nutrition and Exercise Metabolism, 28, 313-315.
  7. Robertson, S., & Mountjoy, M. (2018). A review of prevention, diagnosis, and treatment of relative energy deficiency in sport in artistic (synchronized) swimming. International Journal of Sport Nutrition and Exercise Metabolism, 28, 375-384.
  8. Wilson, G., Martin, D., Morton, J. P., & Close, G. L. (2018). Male flat jockeys do not display deterioration in bone density or resting metabolic rate in accordance with race riding experience: Implications for RED-S. International Journal of Sport Nutrition and Exercise Metabolism, 28, 434-439.

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