What is Relative Energy Deficiency in Sport (RED-S)?


Relative energy deficiency in sport (RED-S) is a condition of low energy availability affecting male and female athletes of all levels and ages.

What is RED-S?

RED-S is the result of insufficient caloric intake and/or excessive energy expenditure.

Who Does It Affect?

It affects both male and female athletes who do not fuel adequately, either intentionally or unintentionally.

Why is it a Problem?

It has wide ranging adverse effects on all bodily systems and can seriously compromise long term health and performance.

Athletes affected by RED-S have openly spoken about consequences such as osteoporosis and its devastating impact on their quality of life and performance.

Consequences of this low-energy condition can alter many physiological systems, including metabolism, menstrual function, bone health, immunity, protein synthesis, and cardiovascular and psychological health.

  • Impaired growth and development.
  • Impact on health and well-being.
  • Adverse effect on performance.


The RED-S concept has been adapted from a previously identified syndrome, the female athlete triad, which affects active women with low-energy availability, menstrual dysfunction and low bone mineral density.

Emerging data suggest there may be a parallel syndrome in undernourished male athletes with resulting hypogonadotropic hypogonadism and impairment of bone health.

As the non-menstrual components are also seen in males, the name was changed to the comprehensive term RED-S.

RED-S is a comprehensive model depicting a low-energy status in physically active women or men.

Why Do Some Athletes Experience Low Energy Availability?

  • Disordered Eating and Formal Eating Disorders:
    • Restricted eating and overtraining may put athletes at risk of developing RED-S.
    • Disordered eating and formal eating disorders exist on a spectrum of eating behaviours.
    • The eating habits of athletes differ from that of non-athletes, and are found closer to the pathological end of the spectrum.
    • Compared with non-athletes, a smaller change in eating behaviour is required for an athlete to develop pathological eating behaviours.
    • There is a 20% higher prevalence of disordered eating in both male and female athletes than in non-athletes.
  • Personality Type:
    • Another reason is an athlete’s personality type.
    • Perfectionism is often seen as desirable in sports people, but it is linked to eating disorders.
    • Athletes are rewarded for, and sometimes picked out as having great potential because of, their “excessive conscientiousness”, “rigidity” and a “preoccupation with details”, all of which are considered pathological under different circumstances.
  • Environmental Pressure:
    • Finally, the pressure an athlete experiences in their environment may result in an eating disorder.
    • Athletes may believe they must look a certain way, eat certain things or do a certain number of training sessions.
    • Pressure to conform to what people expect of an athlete can come from family, friends, the sport more widely, their coach, the media and perhaps most of all, from social media.
  • High Training Load:
    • The prevalence of RED-S is also high amongst athletes who do not suffer from disordered eating.
    • High training load with unintentionally inadequate fuelling or lack of recovery can contribute to RED-S in these athletes.

Consequently, every athlete should be treated as an individual, and their training must be appropriate for them, taking into account factors such as training experience, physiological maturity, biomechanics, and how they respond to different sessions.

Female Athletes Affected by RED-S

Female athletes who suffer from oligomenorrhea or amenorrhea may be advised that taking the oral contraceptive pill (OCP) will address their symptoms. The OCP masks menstrual disturbance without providing adequate bone protection. In fact, hormone replacement therapy (HRT) provides superior bone protection compared to the OCP. If an athlete chooses OCP for contraception, it is important that this is an informed decision taking into account their risk factors for RED-S and requirement for bone protection.

  • Regular menstrual cycle is a barometer of hormone health.
  • Not starting periods by age 16 or not having periods >6 months requires medical investigation.
  • OCP can mask problems without providing bone protection or addressing underlying cause.
  • Using OCP for contraception needs to be an informed decision by the athlete.

What to Look Out For?

  • Perfectionist tendencies.
  • Disordered/restricted eating.
  • Frequent injuries/niggles.
  • Stress fractures and other soft tissue overuse injuries.
  • Illness.
    • Becoming more frequently unwell or finding it hard to shake off common illnesses or infections.
  • Menstrual dysfunction.
  • Loss of sex drive.
  • Amenorrhea (irregular or loss of a women’s monthly period).
  • Significant weight loss.
  • Fatigue, muscle cramps and general weakness.
  • Dehydration.
  • Stomach and gut related problems (gastrointestinal).
  • Dizziness when changing postures (osteostasis).

Consider if you are overtraining, fuelling adequately, and/or taking regular rest days.

Why Seek Support/Medical Help?

There are two main reasons why you should seek help from a general practitioner (GP):

  1. So your GP can rule out other conditions; and
  2. So they can refer on to specialist services (if required).

Other Support

  • There are also initiatives such as #TrainBrave that have been established in an effort to increase awareness of RED-S and combat myths that encourage high risk behaviours amongst athletes – “lighter is faster” for example.
  • The website Health4Performance is another great resource for those wishing to find out more.
  • There is now a specialist NHS RED-S clinic in London that receives support from the National Institute of Dance Medicine and Science (NIDMS).


Dudgeon, E. (2019) Relative Energy Deficiency in Sport (RED-S): Recognition and Next Steps. Available from World Wide Web: https://blogs.bmj.com/bjsm/2019/04/22/relative-energy-deficiency-in-sport-red-s-recognition-and-next-steps/. [Access: 15 January, 2021].

Statuta, S.M., Asif, I.M. & Drezner, J.A. (2017) Relative Energy Deficiency in Sport (RED-S). British Journal of Sports Medicine. 51(21), pp.1570-1571. http://dx.doi.org/10.1136/bjsports-2017-097700.


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