Relative Energy Deficiency in Sport (RED-S)

Relative Energy Deficiency in Sport (RED-S), a syndrome identified and supported by the International Olympic Committee1, characterizes a range of negative health and performance outcomes that result from prolonged (>weeks to months) low energy availability (EA2). Low EA (LEA) is defined as insufficient dietary energy intake in relation to energy cost of exercise, ultimately failing to cover the energy cost to optimally support other important body functions (e.g. growth, recovery, bone health etc.). An athlete may develop LEA and subsequently, RED-S intentionally (eating disorders, disordered eating behaviour, or failed attempts to manage body weight and composition) or by accident (inability or lack of knowledge to consume a sufficient amount of calories to match high training loads3). Prolonged LEA is known to impair endocrine function (low female and male sex hormones), bone health (including upwards of a 4.5x increased risk of stress fractures in elite runners4) as well as have negative effects on the cardiovascular system, illness and injury, and performance outcomes1.

Due to its ability to widely affect athlete health and performance, RED-S is currently a challenge amongst all female and male athletes, over all ages and across all sports. In 2019, Own the Podium (OTP) recognized RED-S, along with concussion and musculoskeletal injuries, as one of the 3 key initiatives around Return to Health & Performance and as a result, put together the National RED-S Committee as part of the new High Performance Advisory Council (Performance Sciences).  As further outlined below, the Committee aims to create a national strategy to help prevent, identify/diagnose, and treat RED-S in Canadian athletes. The focus will be specifically in creating a detection toolkit and/or protocols for treatment. Furthermore, the aim will be to educate Canadian athletes, coaches and parents on RED-S and ultimately reduce incidence. Finally, the committee will target specific research to better understand incidence of RED-S in Canada and evaluate intervention strategies to support athlete health and performance.

About the work the program/committee is doing

The Committee is currently working on: 

  • Creating a RED-S website to educate and increase awareness of RED-S among athletes and their support team
  • Creating an education module aimed at athletes as well as health care practitioners with the aim of preventing RED-S and enhancing early treatment of potential RED-S cases
  • Research around the prevalence and symptoms as well as treatment of RED-S in Canadian development and elite athletes across summer and winter Olympic sports with the goal of more efficient early detection via development of novel screening tools as well as evaluate potential treatment strategies for optimal Return To Performance in athletes with RED-S
  • Eventually, based on the work above, the goal will be to create a RED-S Sports Best Practices strategy document that can be appropriately adapted to each sport as required

Frequently Asked Questions

RED-S is an extension of the Female Athlete Triad. The Triad describes a relationship between 3 main factors: 1) low energy availability, 2) menstrual dysfunction and 3) poor bone health in female athletes. RED-S incorporates the elements and existing science of the Triad but emphasizes that this is in fact a much larger phenomenon that can affect both female and male athletes and result in a number of impairments in health and performance, beyond the female reproductive and bone systems.
No. RED-S is a result of long-term LEA and anyone with LEA can develop symptoms of RED-S. Thus, RED-S can and has been reported in female and male athletes, across endurance, aesthetic, weight category, power and team sports. No athlete is immune to the effects of long term LEA; however it is likely that females in general may be more sensitive to the effects of LEA compared to males, due to differences in the endocrine system between sexes.
It can be challenging to diagnose RED-S as research is still developing. Indeed, RED-S is a diagnosis of exclusion and can manifest differently in different individuals. For example, in females, menstrual dysfunction is a relatively common symptom of potential underlying LEA and RED-S, but other possibilities must be considered and follow up with a physician experienced with this diagnosis is recommended.
In females, menstrual dysfunction (no bleeding) for three consecutive months can be a sign of LEA and RED-S. In both sexes, weight loss may be a sign or LEA. Some other symptoms can include poor recovery, fatigue, inability to concentrate, poor or a prolonged plateau in performance and impaired training adaptation as well as changes in sleep and mental health. It is important to understand that not every athlete will necessarily experience all of these symptoms and that other underlying factors may also explain some symptoms (for example, fatigue may be caused by RED-S, but it may also be a result of overtraining or low iron stores). Currently, a medical assessment (which may include blood work) is recommended to help confirm diagnosis.
Yes. An athlete can develop LEA and as a result, RED-S, even if they eat until they are full. This is especially true for some endurance athletes or male team sport athletes who may expend thousands of calories per day in training and without purposefully choosing high-calorie foods, may risk developing LEA. Remember that LEA is an imbalance between energy intake and expenditure, and therefore, either low calorie intake or high training loads, can lead to the development of LEA.
Yes. While weight loss can be an early sign of LEA, not all athletes will lose weight with LEA. This may be due to the fact that the body is very smart in protecting itself from caloric deficit (an adaptation developed a long time ago when food was at time scarce, and humans had to survive long stretches of poor food availability). Therefore, in some athletes, LEA may lead to a condition called metabolic adaptation, where the body will expend fewer calories at rest and during exercise to minimize energy expenditure to match it with lower energy intake from dietary sources. These athletes can still experience the negative consequences of RED-S.


1.Mountjoy M, Sundgot-Borgen JK, Burke LM, et al. IOC consensus statement on relative energy deficiency in sport (RED-S): 2018 update. Br J Sports Med. 2018;52(11):687-97.

2.Loucks AB, Kiens B, Wright HH. Energy availability in athletes. J Sports Sci. 2011;29 Suppl 1:S7-15.

3.Stellingwerff T, Heikura IA, Meeusen R, et al. Overtraining Syndrome (OTS) and Relative Energy Deficiency in Sport (RED‑S): Shared Pathways, Symptoms and Complexities. Sports Med. 2021.

4.Heikura IA, Uusitalo ALT, Stellingwerff T, et al. Low Energy Availability Is Difficult to Assess but Outcomes Have Large Impact on Bone Injury Rates in Elite Distance Athletes. Int J Sport Nutr Exerc Metab. 2018;28(4):403-11.