The Female Athlete Triad and Relative Energy Deficiency in Sports

Written By: Lee Bell

As coaches, we want the best from our athletes, and that can often mean pushing them hard. While we want to see them perform at the highest level they can achieve, we also need to appreciate that their health matters too.

Whether you are a coach, athlete, or parent of a young athlete, protecting the athlete should be your number one goal. Only when proper care has been put in place can you continue to develop and improve performance.

In this article, I will introduce you to the concept of relative energy deficiency in sports (RED-S), and explore you can put measures in place to protect the athlete and yourself from long-term health complications caused by low energy availability.

The Female Athlete Triad

As far back as 1992, the American College of Sports Medicine (ACSM) issued information regarding a model named the female athlete triad. It was proposed as part of their Task Force on Women’s Issues [1].

According to epidemiology studies, the prevalence of certain health disorders are much higher in athlete populations than in the general public, therefore putting athletes at higher risk of developing them. In particular, sports that emphasize aesthetics or lower total body mass, such as gymnastics, figure skating, diving, running, and ballet, see higher incidences of disordered eating in comparison to general population females [2] – and this was the cornerstone of the initial female athlete triad model.

In simple terms, the model aimed to highlight the effect of disordered eating on both reproductive and bone health in female athletes.

The first iteration of the model was characterized as a distinct set of symptoms, specifically in female athletes who were physically active. It had three distinct disorders at its roots.

  • Disordered eating
  • Amenorrhea
  • Osteoporosis



                                                           Initial Female Athlete Triad Model

Highlighting how severe these issues are from a statistical point of view, up to 69% of female athletes show symptoms of secondary amenorrhea, in comparison to 2-5% in the general public [3,4]. Additionally, as many as 70% of female athletes competing in sports requiring weight classes and 27% of female athletes show signs of disordered eating regardless of sporting event [5].

According to the triad, not all three disorders needed to be present for the athlete to suffer the consequences of ill health. In fact, when matched to general population, there isn’t actually much difference in terms of presenting all three factors simultaneously [6]. But if one or two are present, then long-term health risk increases steeply.

The first iteration of the female athlete triad went a long way in protecting the health of the female athlete. However, it was somewhat restricted to three factors alone: disordered eating, amenorrhea (abnormal absence of menstruation), and osteoporosis (impaired bone health).

A second, revised, and updated version of the triad in 2007 saw “low energy availability” added to disordered eating. This was to take into account the fact that not all low-energy diets are the consequence of an eating disorder. Osteoporosis was updated to include bone loss which took into account any type of disruption of bone remodelling or accelerated bone resorption. Amenorrhea was also updated, this time to include wider menstrual alterations or disturbances.

                                                         Revised Female Athlete Triad Model

This updated version allowed the new revised triad to take into account a wider range of factors when dealing with symptoms, classifications, and diagnosis. However, it was still not considered to take into account all necessary risk factors.

In 2013, the triad was updated again to expand its inclusion criteria even further [7]. This time, the much more comprehensive model included the same low energy availability and bone health factors as before, but also cited “functional hypothalamic amenorrhea” – a disorder that is characterized by a suppressed pulsatile effect on luteinizing hormone and estrogen. This is caused by an increase in exercise energy expenditure. Functional hypothalamic amenorrhea is essentially a catch-all term for any type of menstrual disturbance.

This iteration of the triad also recognized that the associated symptoms do in fact fall along a continuum, something which the previous, more binary versions did not acknowledge. For that reason, a second triangle was proposed that highlighted optimal energy expenditure, bone health, and menstrual cycles. The idea was that the coach or athlete could pinpoint exactly where they were in terms of risk stratification for each of the three factors.

                                                              The 2013 Female Athlete Triad Model

Although much revised, the female athlete triad remains a well-researched and accepted model – partly because of its strong body of research, and partly because there was no similar model at the time to question its authority.

However, it still came under criticism for important omissions in the context of athlete health that were still not included. That is where RED-S comes in.

What is RED-S?

After that whistle-stop tour of the female athlete triad’s history, we arrive at the most up-to-date version of athlete health risk stratification and low energy availability.

In 2014, the International Olympic Committee (IOC) released a consensus statement outlining relative energy deficiency in sports, or RED-S for short.

It was an attempt to update and introduce a broader, more comprehensive term for the female athlete triad – one which considered the multi-factorial nature of athlete health risk.

For the first time it also took into account the fact that some of these factors don’t affect only females, but males too. The RED-S model refers to the consequences of “energy deficiency relative to the balance between dietary energy intake and energy expenditure required for health and activities of daily living, growth and sporting activities” [8].

Simply, it is the impairment of performance and physiological function caused by low relative energy deficiency.

How Does RED-S Differ From The Female Athlete Triad?

According to the IOC, “relative energy deficiency implies that low energy availability occurs when an individual’s dietary energy intake is insufficient to support the energy expenditure required for health, function, and daily living, once the cost of exercise and sporting activities is taken into account”. RED-S not only includes the backbone features of low energy and impaired menstrual and bone health, but other factors that impede both health and performance. These range from increased risk of injury to decreased glycogen storage and diminished training response.

The most obvious difference, as we’ve already discussed, is that the model emphasizes all athletes, not just females (apart from menstrual disruption).

As a caveat, it’s worth mentioning that there are some (The Female Athlete Triad Coalition in particular) that feel the new RED-S model does not in fact improve on the female athlete triad [9]. This is because they feel that the major backbone of the framework – the primary three factors – have been lost within complicated, additional considerations.

The RED-S Conceptual Framework

Within the IOC conceptual framework are a number of symptoms relating to low energy availability and performance decrement. These build on the symptoms discussed in the female athlete triad model and include:

How Does RED-S Affect Performance?

When an athlete trains hard, they require higher nutrient intake to maintain energy homeostasis. When their energy input does not match their needs (total daily energy expenditure, or TDEE – training, physical activity, NEAT, basal functions), low energy availability occurs.

While this is fine for short periods – for example, if the athlete needs to cut weight or lose excess fat – longer periods of energy deficit will begin to affect performance. When this happens, a myriad of symptoms will eventually occur. These include a range of psycho-physiological side effects relating to endocrine, cardiovascular, haematological, immunological, and psychological disorders.

The purpose of defining RED-S isn’t to focus just on the female athlete triad-related symptoms. Rather, it is to take into account wider concerns over negative changes to health and performance physiology. Of course, these include menstrual function and bone health as per previous iterations, but also issues relating to metabolic rate, protein synthesis, and immune function. It is a more holistic attempt to protect athlete health, longevity, and performance.

Assessing the Athlete Using RED-S

As you can imagine, multi-factorial syndromes can be difficult to define, and even more so to pinpoint specific triggers and causes. Bridging the science with a practical setting has always been considered a challenge.But without practical application, models like this are useless unless they have transferable (and easy-to-use) frameworks of diagnosis and treatment.

To combat this, the IOC released a functional clinical assessment tool named RED-S CAT in 2015, although it has actually been in use since 2012 [10]. It is used as a framework and guide for assessing athletes’ “return to play” status. This assessment tool was devised to help coaches identify those at risk of long-term health issues, as well as facilitate treatment and management of return-to-play decisions. The REDS-CAT diagnosis tool uses a simple return-to-play (RTP) rating that clinicians, nutritionists, and other sports medicine professionals can use alongside their specialized knowledge and clinical experience to safely allow athletes to return to sporting competition.

“Green”ratings simply mean that the athlete is at low risk and full sport participation is fine. They are considered to be healthy and have an appropriate physique and body weight.

“Yellow” ratings should invoke caution and as such, a closer analysis of the athlete is recommended. They exhibit some health concerns such as prolonged abnormally low body fat, prolonged energy deficiency, or an abnormal menstrual cycle. Energy output and intake should be thoroughly assessed, as well as training load. The athlete may continue to train, although return to play can only commence once cleared by medical staff. Re-evaluation should take place between 1-3 months to ensure recovery.

Those athletes classed “red” require immediate medical intervention. They exhibit a clinical eating disorder or ECG abnormality. This means no training or competition should take place and all attention should be given to assisting recovery, be it physiological or psychological.

You can find a copy of the RED-S CAT for your own use here.   This external link is a free-to-use download for clinicians.


  1. Marcason, W. Female athlete triad or relative energy deficiency in sports (RED-S): Is there a difference? J Academy Nutr. Diet. 2016; 116(4): 744
  2. Coelho, GM et al. Are female athletes at increased risk for disordered eating and its complications? 2010 Dec; 55(3):379-87.
  3. Abraham, SF et al. Body weight, exercise and menstrual status among ballet dancers in training. Br J Obstet Gynaecol. 1982; 89(7): 507-10
  4. Dusek, T. Influence of high intensity training on menstrual cycle disorders in athletes. Croat Med J. 2001 Feb; 42(1):79-82
  5. Coelho, GM et al. Prevention of eating disorders in female athletes. Open Access J Sports Med. 2014; 5: 105-113
  6. Torstveit, MK et al. The female athlete triad exists in both elite athletes and controls. Med Sci Sports Exerc. 2005; 37(9): 1449-59
  7. Barrack, MT et al. Update on the female athlete triad. Curr Rev Musculoskeletal Med. 2013; 6(2): 195-204
  8. Mountjoy, M et al. The IOC consensus statement: beyond the female athlete triad—relative energy deficiency in sports (RED-S). Br J Sports Med. 2014; 48(7): 491-7
  9. De Souza, MJ et al. Misunderstanding the female athlete triad: refuting the IOC consensus statement on relative energy deficiency in sport (RED-S). Br J Sports Med. 2014; 48(20): 1461-1465
  10. Mountjoy, M et al. The IOC relative energy deficiency in sport clinical assessment tool (RED-S CAT). Br J Sports Med. 2015; 0: 1


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