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RED-S: an updated discussion.

Once known as the Female Athlete Triad, RED-S includes the previous concepts of the Triad (disordered eating, menstrual dysfunction and reduced bone density) but acknowledges the extensive impacts energy deficiency has on the entire body and is inclusive of male athletes.

The underlying cause of relative energy deficiency in sports (RED-S) is low energy availability (LEA) to support optimal body functions required for health and performance. Low energy availability may be due to failure of meeting high energy needs (unintentional), disordered eating behaviours (intentional), or specific weight control programs (misguided but intentional). Unintentional LEA is more straightforward to resolve as it typically requires educating an athlete on the sheer quantity of food required to support their training load and/or active lifestyle/job. This may be the result of an amateur athlete suddenly ramping up their training load in addition to an active lifestyle/job whom is not under the supervision of a coach and/or nutrition professional. Generally recreational athletes do not have the expertise of a team around them as would an elite athlete (e.g., coach, dietitian, physiotherapist, sports doctor, psychologist). When LEA is intentional, it becomes a bit more complicated as this typically involves disordered eating. Disordered eating is a continuum which starts with healthy eating behaviours and a positive relationship with exercise, and at the opposite end includes full-blown diagnosed eating disorders such as bulimia and anorexia nervosa (as per the DSM-5 diagnostic criteria). This requires much more intensive treatment and an approach that includes not only the dietitian, but the wider multidisciplinary team including a psychologist with experience in eating disorders and athletes.

RED-S can occur to any athlete of any gender and is not limited to the elite. In fact, weekend warriors or recreational athletes are at greater risk because they may not have as much awareness of RED-S or the sporting experience and knowledge an elite athlete may have. However, RED-S is typically more common in sports where power to weight ratio is key, where body aesthetics are a focus, or body weight classes are a requirement for competing. Some examples include jockeys, long-distance running, weight lifting, combat sports, rowers, dancers, gymnasts, and cyclists. In male athletes, it has been specifically noted that road cyclists, rowers (both lightweight and open), combat sports, endurance runners, and jockeys are at heightened risk. Common risk factors in these sports are due to management strategies around ‘making weight,’ and the high energy cost of training programs that are not always easily matched by energy intake. Food insecurity can also be a contributing factor to some athlete’s accessibility to adequate food in certain population groups (1). Figure 1. illustrates how RED-S can impact multiple body systems.

Figure 2. illustrates the signs and symptoms of RED-S that athletes may experience.

What RED-S may also look like:

  • Frequent sickness

  • Recurring injuries or injuries not healing (especially stress #)

  • Menstrual dysfunction (amenorrhea - in females)

  • Reduced testosterone (males)

  • Loss of libido

  • Low mood/irritability/withdrawn

  • Fatigue and lethargy

  • Always feeling cold

  • Disordered eating behaviours and preoccupation with food

  • Low bone density and increased risk stress fractures

  • Digestive issues, particularly constipation

  • Weight loss or weight maintenance are both possible

It is important to note, screening for RED-S can be challenging as symptoms may be subtle. There are also no standardised guidelines to determine the energy availability of athletes, as even the initial equation mentioned in this discussion requires expertise and even then, the results may be imprecise. A female athlete may show signs of RED-S but maintain her menstrual cycle. It is really important female athletes are aware that certain types of contraception can mask underlying menstrual disturbance. For example, oral contraceptive pills elicit ‘withdrawal bleeds’ (fake periods) whilst other forms of contraception including the Mirena IUD or the depo Provera injection often cause amenorrhoea due to their mode of action. This can make it very hard for both the athlete and clinician to get a clear picture of menstrual health, which is one of female athletes best ‘report cards’ of overall well-being each month. Another important consideration is athletes may maintain their body weight but still experience RED-S. If an athlete has lost weight and is showing other symptoms of RED-S then this would certainly warrant further investigation.

In a study (2) looking at elite rowers in a 4-week intensive training period it was found that resting metabolic rate (RMR) and relative RMR was significantly reduced (5%) between the start and of end of the training block. Additionally, there were significant decreases in body mass and fat mass (note: hydration levels stable). There was also a notably significant increase in fatigue and mood disturbance. This data would suggest an energy imbalance as although there was an increased training volume, the rower’s energy intake remained mostly unchanged which is of concern with regards to LEA and the risks this can have on athletes’ health and performance. This study highlighted that RMR may be an early indicator of training disturbance alongside changes in psychological markers. However, RMR in the typical athlete population can be challenging to accurately assess outside of laboratory or research environments.

What is the treatment for RED-S?

Diagnosis of RED-S requires a multidisciplinary team approach and medical intervention is vital. If left untreated, sickness or injury will force the athlete to take a long period of time off training to let their body recover appropriately. Worst-case scenario the individual may suffer long-term health consequences (e.g., impacts on fertility and bone health (osteoporosis)) or be forced to retire from their sport.

The treatment typically involves an increase in energy intake, a reduction in energy expenditure (i.e., reduced training volume), or more often than not a combination of both. Increased energy intake may be as simple as an extra 200 calories per day (e.g., an extra snack) up to a more significant increase (600 – 800 calories +). For those recovering from RED-S I would never expect them to completely cut out exercise as the impact this could have on mental wellbeing could be detrimental to overall well being. It is important to find the happy medium between the athlete, clinician, and coach around acceptable training volume and energy intake. The exception of this is if the athlete is severely unwell due to an eating disorder and it is simply not safe for them to exercise, or they have an injury that requires complete rest (e.g., a serious stress fracture). If an athlete is failing to improve from RED-S or is not adhering to strategies then there may be underlying psychological factors (i.e., significant disordered eating) and expertise from a mental health practitioner needs to be integrated into the treatment plan (3).

1. International Journal of Sport Nutrition and Exercise Metabolism, 2018, 28, 364-374.

2. Woods AL, Garvican-Lewis LA, Lundy B, Rice AJ, Thompson KG (2017) New approaches to determine fatigue in athletes during intensified training: Resting metabolic rate and pacing profile. PLos ONE 12(3): e0173807.

3. Mountjoy M, Sundgot-Borgen J, Burke L, et al. Br J Sports Med 2014;48:491-497.


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