Relative Energy Deficiency in Sport (RED-S)

How Does it Relate to Eating Disorders?

Mary Cain and Relative Energy Deficiency in Sport

Christian Petersen, Getty Images Sport 

In a recent Opinion piece for The New York Times, “I Was the Fastest Girl in America, Until I Joined Nike,” Mary Cain details how her Nike track coach Alberto Salazar encouraged her to lose weight to become faster. Instead of increasing her speed, she developed relative energy deficiency in sport (RED-S) which resulted in low estrogen and weakened bone strength. She did not menstruate for three years and broke five different bones.

What is relative energy deficiency in sport? And how does it relate to eating disorders? How common is it?


RED-S was first introduced as a term by the International Olympic Committee (IOC) in 2014. It is a syndrome that results from energy deficits in athletes. The IOC described RED-S as “a syndrome that affects many aspects of physiological function, health, and athletic performance.”

The underlying problem in RED-S is an energy intake inadequate to support the range of body functions required for health and performance.

Athletes typically have higher energy needs than non-athletes. In RED-S an athlete is eating too little relative to the energy they expend and various bodily functions are negatively impacted, including the gastrointestinal, immunological, endocrine, metabolic, hematological, and cardiovascular systems.

RED-S is a term replacing an earlier one used to describe the same conditions. Energy deficiency in sport was previously thought to be only a female problem and was called the female athlete triad. The female athlete triad was first described in 1997 by the Task Force on Women’s Issues of the American College of Sports Medicine. The female athlete triad refers to three linked problems: energy deficiency, menstrual dysfunction, and bone loss. In recognition that male athletes were also affected, RED-S replaced the female athlete triad.

How Common is RED-S?

Prevalence rates of RED-S are not well-established. RED-S is a new syndrome—only defined in 2014—so research is limited. Additionally, many athletes may be unwilling to report a problem or might be unaware of a problem given the focus on performance and thinness in many sports where dieting and restricting are encouraged.

The rates of eating disorders in athletes have been somewhat better investigated. Most studies to date have studied female athletes. Compared to non-athlete peers, female athletes report eating disorders at a higher rate: 18% to 20% compared to 5% to 9%. Prevalence rates of the entire spectrum of eating disorders and subclinical disordered eating vary from 0 to 19% in male athletes and from 6 to 45% in female athletes. The prevalence varies significantly among different sports.

Risk Factors

RED-S can affect athletes of any age and gender. Although any athlete can suffer from RED-S, those at greatest risk are those in judged sports with an emphasis on appearance or aesthetics (such as gymnastics or figure skating), weight category sports (such as crew), and endurance sports (such as cross country).

Although there appears to be an increased risk of disordered eating—and therefore RED-S—among athletes, there is not enough research to draw strong conclusions on who is most at risk among athletes. However, there are some factors that may increase risk.

Revealing Outfits

For example, the requirement to wear revealing clothing in sports such as volleyball and swimming is believed to play a role by heightening body surveillance, comparisons with others, and promoting body dissatisfaction. Other factors can be the pressure of weight requirements in certain sports that increase preoccupation with weight and reinforce dieting.

Coach Expectations

Additionally, the pressure and influence of coaches—such as the pressure that Mary Cain describes from Alberto Salazar—can be a contributory factor. It is important to acknowledge that coaches and other sports professionals can have a positive impact if they promote adequate fueling and early identification and management of eating problems among their athletes.

Symptoms and Diagnosis

Diagnosis of RED-S can be challenging, as symptoms can be subtle. Symptoms can vary among athletes and may include:

  • Fatigue
  • Weight loss
  • Dehydration
  • Lack of normal growth and development
  • Muscle loss
  • Poor concentration and coordination
  • Recurrent injuries and illnesses
  • Decreased performance
  • Mood changes

In the case of athletes who should be menstruating the menstrual cycle is an obvious clinical indicator of sufficient energy availability. There exists no such obvious clinical sign in athletes who physically cannot menstruate which may be why RED-S has been less frequently recognized among cis men and trans women and perceived as a "female" problem.

The RED-S CAT is a clinical assessment tool for the evaluation of athletes and active individuals suspected of having relative energy deficiency and for guiding return to play decisions. If you or someone you know is suspected of having RED-S they should have a thorough medical examination.


Ironically, while weight loss may often be undertaken as an effort to increase athletic performance, as in the case of Mary Cain, the ultimate consequence may be decreased athletic performance as well as serious deleterious consequences for many bodily systems. In other words—the exact opposite effect of what an energy restricting athlete is aiming to achieve. They may experience reduced responsiveness to training and subsequent decreased performance.

The consequences of RED-S can be very similar to those of anorexia nervosa. Athletes may develop nutritional deficiencies, chronic fatigue and increased risk of infections and viral illnesses. They can be at risk for cardiovascular problems. RED-S can also make bones more fragile.

Failure to adequately fuel can lead to hypothalamic amenorrhea in athletes who physiologically can menstruate. Low availability of sex hormones in athletes of all genders with RED-S can lead to low bone mineral density which places athletes at increased risk for stress fractures. This bone loss can be irreversible and can lead to osteoporosis.

RED-S and Eating Disorders

RED-S may overlap with an eating disorder, be the result of an eating disorder, or can be a risk factor for an eating disorder. By definition, the syndrome results from undereating.

Disordered eating exists on a continuum that ranges from an appropriate balance between eating and exercise at one end, to a full clinical eating disorder at the other end, with disordered eating or undereating sitting in the middle.

The disordered eating can be either an intentional nutritional restriction to control body weight and composition, or an unintentional consequence of not matching an increase in energy expenditure stemming from an increased training load with a commensurate increase in energy intake. Even when an eating disorder is not present, RED-S can have a psychological impact.

How is it Treated?

Treatment for RED-S should involve an increase in dietary intake, a reduction in exercise, or both. Energy-rich supplemental drinks and exercise rest days are often initial steps. In collegiate athletes, weight gain is the strongest predictor of resumption of normal menstrual function. Oral contraceptives are not recommended for the treatment of RED-S because they do not reduce bone loss and can mask low energy availability and menstrual dysfunction.

When an athlete is unable to follow the treatment recommendations to increase intake, decrease activity level, and gain weight, then psychological factors such as an eating disorder may be considered to be a factor. According to the IOC consensus statement, “Athlete resistance to treatment usually increases with the severity of the eating problem.”

When an eating disorder is suspected or involved, treatment should involve a multidisciplinary team including a medical doctor, registered dietitian, and mental health therapist well versed in eating disorders and sports. This team should coordinate closely with the athlete’s coach or trainer. Treatment is usually required for several months.

Many athletes may need to take a complete break from their sports training depending on the severity of the eating issues and medical consequences. The IOC has developed a return-to-play model that determines an athlete’s readiness to return to their sport.

A Word From Verywell

If you are an athlete, recognize that getting adequate intake relative to energy expended is critical for optimal health and athletic performance. If a coach is pressuring you to lose weight to increase performance, consult with other experts. Recognize that loss of menstruation due to training is not normal and a warning sign. If you are unsure about your energy needs, consult a registered dietitian. 

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  • Cain, M. 2019. Opinion: I Was the Fastest Girl in America, Until I Joined Nike.  The New York Times.

  • Dudgeon, Emily. Relative Energy Deficiency in Sport (RED-S): Recognition and next Steps BJSM Blog. April 22, 2019.

  • Keay, N. 2018 UPDATE: Relative Energy Deficiency in Sport (RED-S) BJSM Blog. May 30, 2018.

  • 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. RED-S CAT. Relative Energy Deficiency in Sport (RED-S) Clinical Assessment Tool (CAT). Br J Sports Med. 2015 Apr;49(7):421-3.

  • Mountjoy M, Sundgot-Borgen J, Burke L, Carter S, Constantini N, Lebrun C, Meyer N, Sherman R, Steffen K, Budgett R, Ljungqvist A. The IOC consensus statement: beyond the Female Athlete Triad– Relative Energy Deficiency in Sport (RED-S). Br J Sports Med. 2014 Apr;48(7):491-7. 

  • Plateau, C. R. and Arcelus, J. 2018. Eating Disorders in Athletes: Detection, Diagnosis, and Treatment. 384-398. Clinical Handbook of Complex and Atypical Eating Disorders. 60-78. Oxford University Press. New York.

By Lauren Muhlheim, PsyD, CEDS
 Lauren Muhlheim, PsyD, is a certified eating disorders expert and clinical psychologist who provides cognitive behavioral psychotherapy.