• Yurika Tarui

Relative Energy Deficiency in Sport - What is it? RED-S Series Part 1!

Updated: Jun 29


Deep down, something isn’t right.


Your bones ache. Your body is heavy with constant exhaustion. Your mind is in a perpetual fog.


On the surface, you’re the perfect athlete. You’re eating “well.” You’re training diligently. You’re playing hard.


All your teammates and coaches compliment you on your passion and commitment, encouraging you to keep going.


The nagging voice in your head yells at you to brush it off, toughen up, push through.


Yet, part of you, the intuition in you, knows that something is wrong.


That intuition is often right: you likely are suffering from Relative Energy Deficiency in Sport or RED-S.


Thousands of athletes from all backgrounds suffer from this syndrome, often without even knowing it.


Unfortunately, most athletes will never receive a formal diagnosis, let alone learn about the syndrome in the first place.


And the consequences aren’t pleasant; from heart irregularities to osteoporosis, decreased strength to overuse injuries, RED-S can be potentially career-ending or even life-threatening.


Even if it doesn’t reach that point, athletes will experience compromised mental and physical wellbeing, affecting their lives on and off the field.


If we want to create a sports community that is safe, supportive, and productive, we need to advocate for athlete health. And that requires raising awareness and breaking the stigma surrounding RED-S.


In Part 1 of our RED-S series, we’ll be covering the basics of RED-S, its symptoms and causes, and how it impacts athletes. Later articles will cover how to prevent and treat RED-S, common misconceptions, and potentially some interviews!


Bookmark this article for future reference and share it with your friends! Education is the key to prevention, and you have the power to change the narrative!



What is RED-S?


RED-S is a medical syndrome where a chronic energy deficiency in athletes causes mental and physical complications. Officially coined by the International Olympic Committee in 2014, it is a new syndrome being researched and addressed within the sports community.



What causes RED-S?

RED-S’s primary cause is underfueling relative to energy expenditure, which can come from undereating, overexercising, or a combination of the two. Note that underfueling can be intentional or unintentional. Even if an athlete is eating a “normal” amount of food and not deliberately restricting their intake, they can still be underfueling their bodies. (1)

While not always the case, disordered eating or eating disorders in athletes can cause RED-S by triggering the energy deficit. There can also be underlying medical issues or genetics that predispose an athlete to enter an energy deficit.


Who develops RED-S?


Anyone of any gender playing any sport at any body size can develop RED-S, even elite football players! (2)

Contrary to popular belief, it is not a syndrome exclusive to thin women in aesthetic sports. However, athletes participating in aesthetic, endurance, and weight-class sports are at higher risk.



Some of these sports are:

  • Figure skating

  • Dance

  • Gymnastics

  • Acrobatics

  • Diving

  • Horseback riding

  • Wrestling

  • Bodybuilding

  • Weightlifting

  • Rowing

  • Running

  • Swimming

  • Cycling

  • Skiing (especially Nordic and ski jumping) (2)

Those with histories of disordered eating, eating disorders, and previous RED-S experiences are also at higher risk.


What are the symptoms of RED-S?


There are various RED-S symptoms, both physiological and psychological, and each athlete experiences them differently. Some common symptoms include:

  • Amenorrhea (2)

  • Delayed puberty (2)

  • Growth stunting (2)

  • Falling off one’s growth curve with weight, height, or BMI

  • Gastrointestinal issues (bloating, constipation, gas, etc.)

  • Weight loss (2)

NOTE: Not everyone with RED-S experiences weight loss! In fact, when people have struggled with RED-S for extended periods, their body slows down their metabolism to conserve energy and prevent further weight loss, plateauing their weight.

  • Muscle cramps, weakness, fatigue (1)

  • Stress fractures and other overuse injuries (1)

  • Low bone density (1)

  • Dehydration

  • Cardiac issues (bradycardia, orthostatic hypotension) (1)

  • Cold intolerance (1)

  • Hormonal imbalances (1)

  • Irregular eating behaviors (1)

  • Increased anxiety and depression (1)

  • Rigid attitudes surrounding exercise (2)

  • Distorted body image (1)

  • Loss of concentration (2)

  • Libido (3)

  • Sleeping issues (2)

  • Performance decline and increased errors (2)

  • Vitamin/mineral deficiencies (2)

  • Pelvic floor dysfunction (ex. Urinary incontinence) (6)


Why should athletes care about RED-S?


While many athletes with RED-S go undiagnosed, it has substantial consequences for both an athlete’s health and athletic performance.


Medical and psychological consequences

Imagine this: Your expenses are high, but your paycheck isn’t enough to cover everything, and your bank account is rapidly depleting. Would you continue spending money at that rate, or would you cut back on your expenses as much as possible, to stay afloat?


The human body is the same: when it falls into a long-term energy deficit, it must conserve as much energy as possible. Your body enters survival mode - its only goal is to stay alive. Unfortunately, this means cutting back on resources needed for vital organs, including your brain and heart. Some consequences are listed below:

  • Hypothalamic amenorrhea (2)

  • Fertility issues (2)

  • Decreased hormone production - testosterone, estrogen (2)

  • Decreased metabolism (2)

  • Low bone density → osteopenia, osteoporosis (2)

  • Increased risk of stress fractures (2)

  • Increased risk of injuries (2)

  • Cardiac issues, including bradycardia and orthostatic hypotension (2)

  • Pelvic floor dysfunction (6)

  • Decreased muscle mass (2)

  • Weakened immune system (2)

  • Depression and anxiety (2)

  • Disordered eating and eating disorders (2)


Performance consequences


When your body is in survival mode, as it’s in an energy deficit, the last thing it can do is spend its limited resources on movement. Multiple studies corroborate that RED-S negatively impacts athletic performance:


> In a 12-week training program for female swimmers ages 15-17, those with regular menstrual cycles saw an 8.2% increase in velocity. However, those without regular cycles saw a 9.8% decrease in velocity, along with decreased ovarian and metabolic hormones. (2) [Van Heest 2014]



> After a 4-week heavy training program with elite Australian rowers, the rowers experienced a decreased resting metabolic rate, body composition changes, and increased fatigue. Additionally, their ability to maintain velocity during 5k time trials decreased compared to before the heavy training. [Woods 2017]


> A study of British jockeys discovered that jockeys that lost 2% of body mass through dehydration on average experienced a 13.8% decrease in chest strength, a 4.8% decrease in leg strength, and a 2.8% decrease in simulated performance. Jockeys who did not lose weight experienced marginal changes in performance: a 0.62% increase in chest strength, a 0.56% decrease in leg strength, and a 0.07% decrease in simulated performance. [Wilson et al., 2014b]


Countless anecdotes from athletes have also shown the adverse effects of RED-S on athletic performance. We are hoping to interview some athletes on their experiences in upcoming posts!


In summary


> RED-S is a medical syndrome where a chronic energy deficiency in athletes, either intentional or unintentional, causes mental and physical complications.

> Symptoms vary by person, but some common ones include amenorrhea, low bone density, stress fractures, and disordered eating.

> Multiple studies have shown that RED-S hinders athletic performance.


In the next installment of the RED-S series, we’ll be discussing how to prevent and treat RED-S! Bookmark our blog, subscribe to our mailing list, and follow us on Instagram to be notified of the next article!



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