What is ‘RED-S’ and why should you care?

Written by Student Dietitian, Sports Nutritionist & Personal Trainer – Nadia Ford
Pictured at Tongariro, New Zealand
RED-S (Relative Energy Deficiency in Sports) is more than just a mysterious condition experienced by the odd elite-level athlete. In fact, RED-S is a surprisingly common and often undetected condition that may affect female and male athletes at various levels of training and competition, (1) of which arises due to ‘low energy availability’ (a mismatch between our body’s nutrition needs and what we’re feeding it) (2).
It turns out, our body is very good at adapting to undernutrition, so when it is underfed for prolonged periods, it begins to down-regulate functions that it deems unnecessary for imminent survival (2). This has a range of adverse impacts on all body systems, which can have the following consequences (2).
  • Declined reproductive functioning and health
  • Impaired bone health and greater risk of bone fractures
  • Impaired growth and development
  • Poor gut health and gastrointestinal disturbances
  • Declined immune function leading to greater risk of infection and illness
  • Iron deficiency
  • Heart disease


So, who is at risk?

The more elite an athlete is in their sport, the greater their overall training load and the greater their subsequent energy requirements. This suggests that elite athletes should be the most prone to developing RED-S if they are not following a tailored nutrition plan. However, an individual who trains at a lower level, such as recreationally or semi-professionally, will still have increased energy requirements on top of their usual metabolic requirement (the energy required to survive). When this increased requirement is not met – you guessed it – the risk of developing RED-S is accelerated.
Athletes that are particularly prone to developing RED-S include those that are pressured to achieve and maintain a certain physique for their sport, such as gymnasts, figure skaters, martial artists, ballerinas and AFL players. From an AFL athlete perspective (as this is an area we specialise in), an important consideration would be to ensure that periodisation in the training calendar reflects an appropriately matched periodised nutrition plan for individual athletes on the team, (4) and this should be developed, overseen, and regularly monitored by a performance dietitian. All of these athletes, however, regularly face considerable pressure to reach strict aesthetic goals may lead to disordered eating habits, which may therefore increase the risk of under-fuelling, subsequently increasing the risk of developing RED-S.
RED-S may also develop unintentionally in athletes who do not have the nutritional support of a performance dietitian, or a guided nutrition plan to follow, which is often the case with recreational athletes. (3) Without this support, athletes may not realise how to fuel their bodies appropriately for their training and competition loads. Alternatively, an athlete may have been prescribed a nutritional plan, but they may not have the finances to follow through with the plan.

So, what are some risk factors and potential warning signs of RED-S? (3)

  • Increased injury and illness frequency
  • Decreased muscle strength/endurance performance
  • Decreased coordination, concentration, and judgement
  • Decreased enjoyment in sport
  • Increased irritability
  • Depression
  • Menstrual dysfunction
  • Disordered/restricted eating

“I think I’m at risk of RED-S, what should I do?”

Book in as soon as possible with a medical doctor, and ideally seek referral to a specialist medical doctor that manages RED-S in athletes as well as a specialist sports or performance dietitian.
1. Dudgeon E. Relative energy deficiency in sport (RED-S): British Journal of Sports Medicine [Internet]. 2019 Apr 22; Available from:
2. Mountjoy M, Sundgot-Borgen JK, Burke LM, Ackerman KE, Blauwet C, Constantini N, et al. IOC consensus statement on relative energy deficiency in sport (RED-S): 2018 update. Br J Sports Med [Internet]. 2018;52(11):687–97. Available from:
3. Relative energy deficiency in sport [Internet]. High Performance Sport New Zealand. [cited 2021 Nov 29]. Available from:
4. Maughan R, Burke L. Nutrition for athletes: A practical guide to eating for health and performance [Internet]. International Olympic Committee Medical and Scientific Commission; 2012. Available from:

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