It is widely understood that athletes need to fuel themselves to have energy for their sport. When this fueling does not meet the demand of the energy that the athlete is expending, the athlete becomes at risk for what is called Relative Energy Deficiency in Sport (RED-S). While this term has been used for over 10 years, the awareness and understanding of this syndrome and its implications for athletes are low.
What is Relative Energy Deficiency
Relative Energy Deficiency, or, RED-S is a syndrome that is caused by one being in a prolonged or severe state of low energy availability due to inadequate nutrients being consumed relative to the athlete’s energy output during their daily and sport-related activities. This can result from low nutritional intake and/or excessive energy expenditure; however, studies have shown that the most likely reason is low nutritional intake. Further, recent studies have shown that inadequate carbohydrate intake has contributed to this low-energy availability state.
There are several factors that may put an athlete at risk for RED-S. Athletes who participate in endurance, aesthetic, and weight-class sports such as cross-country/track and field, dance, gymnastics, swimming, or wrestling may be at greater risk due to pressure to maintain a light weight or smaller physique. This pressure may come unintentionally from coaches, peers, family, social media, and the elite/professional athlete population. This is especially concerning for developing athletes, where growth is vital and necessary for proper body system functioning.
It is unclear what the exact prevalence of RED-S is because the lack of awareness and inconsistent diagnostic measures have created a wide range in reported prevalence. However, this prevalence ranges from 23-80% in female athletes and 15-70% in male athletes. While this is a large range, the prevalence is undoubtedly high, signifying that this exists and affects many athletes.
How it affects athletes
What makes RED-S so tricky is that initially, an athlete may see improved performance in their sport. In a sport like running, this may start a vicious cycle of positive reinforcement associated with behaviors that lead an athlete to be in a state of low energy availability. However, this performance boost only occurs in the short term. The negative effects of RED-S are delayed, which means an athlete may be adopting harmful behaviors before they are symptomatic.
Before there was RED-S, there was a term called the Female Athlete Triad that was used from 1992 until RED-S replaced it in 2014. The Female Athlete Triad proposed that being in a state of low energy availability is related to disordered eating, menstrual dysfunction (lack of or abnormal periods), and low bone mineral density (osteoporosis and fractures). While these are all part of RED-S, studies are finding that there is much more to this syndrome.
RED-S affects multiple body systems and manifests in several different symptoms. Most notable are a lack of (amenorrhea) or abnormal (dysmenorrhea) period in females, absent morning erection and libido in men, and poor bone health in both men and women. However, RED-S can affect reproductive function, immune function, growth and development, cardiovascular function, cognition, mental health, metabolism, gastrointestinal function, and more, as you can see in the diagram below. The symptoms of RED-S include:
- Bone stress injuries (ie. stress fractures), particularly recurrent injuries
- Fatigue
- Absent or irregular periods in females
- Low libido in males
- Frequent illness
- Loss of strength
- Poor recovery
- Irritability
- Depression and anxiety
- Poor concentration
- Cold intolerance
This is not an exhaustive list, but certainly a long one. To drive the point home further, RED-S affects many aspects of the athlete that not only affect their performance but also their health and if left untreated, it can affect their health in the long term.
Why this matters in the long run
In the long-term, athletes remaining in a state of low energy availability may develop osteoporosis, which is when bones become weaker and are at greater risk for fracture. Fractures can be detrimental to the performing athlete as they force them to take time away from their sport to recover, but it can also affect their future selves as fractures can lead to surgery and reduced function. Athletes with unaddressed RED-S may experience chronic hormonal dysfunction that may lead to a whole host of challenges, such as infertility, pregnancy complications, and chronic disease.
How Physical Therapy can help
It is important to note that treatment for RED-S must be multi-disciplinary in nature. Physical therapists can be most helpful through early identification and screening for RED-S, making referrals to appropriate disciplines such as a physician, dietitian, and sports psychologist, and for management of injuries such as bone stress injuries.
While athletes with RED-S are not limited to solely bone stress injuries, this is the most seen. Physical therapists have expert knowledge of bone health and proper management of bone stress injuries. Due to the nature of the repetitive loading that running requires, cross-country athletes are at the highest risk for bone stress injuries compared to any other sport. It is important to note that para-athletes and swimmers may also be at significant risk for bone stress injuries due to the lack of weight bearing, which can also lead to decreased bone density.
Bone stress injury and bone density management from a physical therapy perspective consists of periods of relative rest and progressive loading. Our bones are constantly remodeling and working to rebuild, especially in our younger years. While athletes may develop osteoporosis at a young age, this can be reversed with proper treatment and guidance. Bone density is built with jump training, such as plyometrics and weight-bearing strength training. Physical therapists can use their knowledge of bone healing and bone load tolerance to guide the patient through bone stress injury recovery and increasing bone density.
Athletes, Coaches, and Parents need to be aware of RED-S as it has both short-term and long-term negative consequences for those who experience it. Not only this, but RED-S impacts athletes’ performance in sport during the height of their athletic careers. While these effects can be reversed, it takes a team of providers to support their recovery. Our staff here at Spark can identify risk factors of RED-S and make necessary referrals, as well as guide athletes back to their sport after injury, such as stress fractures. We must be aware of RED-S to help athletes perform at their best and to stay healthy even beyond the prime of their athletic careers.
References
BMJ Group. (2023, September 26). Prolonged mismatch between calories eaten and burned may be putting many athletes at risk of RED-S. https://www.bmj.com/company/newsroom/prolonged-mismatch-between-calories-eaten-and-burned-may-be-putting-many-athletes-at-risk-of-reds/
Cabre, H. E., Moore, S. R., Smith-Ryan, A. E., & Hackney, A. C. (2022). Relative energy deficiency in sport (RED-S): Scientific, clinical, and practical implications for the female athlete. Deutsche Zeitschrift für Sportmedizin, 73(7), 225–234. https://doi.org/10.5960/dzsm.2022.546
Logue, D. M., Madigan, S. M., Melin, A., Delahunt, E., Heinen, M., Donnell, S. M., & Corish, C. A. (2022). Low energy availability in athletes: A review of prevalence, dietary patterns, physiological health, and sports performance. Sports Medicine, 52(Suppl 1), 27–46. https://doi.org/10.1007/s40279-021-01539-3
Mountjoy, M., Ackerman, K. E., Burke, L. M., Hackney, A. C., Heikura, I. A., Pensgaard, A. M., & Stellingwerff, T. (2023). International Olympic Committee (IOC) consensus statement on Relative Energy Deficiency in Sport (RED-S): 2023 update. British Journal of Sports Medicine, 57(17), 1073–1097. https://doi.org/10.1136/bjsports-2023-106994
Zwickl, H., Zwickl-Traxler, E., Haushofer, A., et al. (2024). Impact of relative energy deficiency in sport (REDs) on bone health in elite athletes: A retrospective analysis. [Journal name not clearly specified in PMC version]. https://doi.org/ (if available) or https://pmc.ncbi.nlm.nih.gov/articles/PMC12485273/