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Updated: Nov 11, 2022

What is RED-S?

Relative energy deficiency in sport (RED-S) is the result of insufficient caloric intake and/or excessive energy expenditure (energy) (1,2). RED-S was previously known as the ‘Female Athlete Triad’. The International Olympic Committee (IOC) updated the IOC Consensus Statement on the Female Athlete Triad in 2005. This Consensus Statement replaced the previous guidelines and introduced new guidelines on how to carry out risk assessments, treatment and return to play decisions. The IOC wanted to introduce a broader, more comprehensive term for the condition to include male athletes as they are also affected by this condition (1).

RED-S refers to the impaired physiological function including, but not limited to, metabolic rate, menstrual function, decreased bone health (bone mineral density), immunity, protein synthesis, cardiovascular health caused by relative energy deficiency (1).

RED-S is the relationship between Low Energy Availability (LEA), hormonal dysfunction and low bone mineral density. Low energy availability occurs when there are not enough calories remaining to provide energy required for health, function and daily living, once the cost of exercise is subtracted. It can be a result of an eating disorder, disordered eating or under fuelling.

For female athletes, low energy availability can result in low oestrogen and potentially amenorrhoea (the absence of the menstrual cycle for 3+months). For male athletes, low energy availability can result in low testosterone produced (3). Both low energy availability and hormonal dysfunction impact bone mineral density. Athletes with RED-S are at risk of developing weakened bones, osteoporosis and an increased risk of stress fractures.

Signs, symptoms and impact of RED-S

People who are at a high risk of this syndrome are vegan/vegetarian athletes, young athletes going though growth and development and athletes in weight class or aesthetic sports like endurance athletes, cycler, climber, gymnasts, swimmers (3). Signs of someone who may have RED-S include excessive fatigue, menstrual dysfunction, females who haven’t got their period by the age of 16 and/or excessive exercising. Potential symptoms of RED-S include muscle loss, hair loss, dry, cracked skin and mood changes.

RED-S can have major implications on the body systems and have negative effects on an athletes optimal health and athletic performance (3). It can decrease endurance, strength, coordination, concentration, impaired judgement and may have difficulty recovering.

Assessment of RED-S

There is no clear-cut criteria of assessing energy availability however, it is suggested to use the RED-S Clinical Tool. There are two types:

  1. RED-S Risk Assessment Model

  2. RED-S return to Play Model (1,3)

The prevention of RED-S requires increased awareness among athletes. To prevent and treat an individual with RED-S, it is best to have a multidisciplinary approach in place including medical, dietary and mental health support (3).

The IOC recommends educational programmes for athletes on RED-S and nutrition, to reduce the emphasis on weight and emphasise more on nutrition and health and to avoid critical comments on someone’s weight and body size (3). It is important to educate athletes of the signs and health effects of eating disorders and to educate coaches as well.

If a female athlete has lost their menstrual cycle, it is essential to try and restore menstruation and bone mineral density by gradual increasing their energy availability. The aim for treating an individual with RED-S is to increase energy availability by increasing energy intake and/or reducing exercise energy expenditure (2).

Disordered eating and eating disorders are more prevalent among female and male athletes in weight-sensitive sports. Nutrition counselling may be needed for some athletes to focus on approaching food and building a good relationship with food.

It is critical to detect the risk of energy deficiency of athletes in the early stages to prevent long-term health consequences. Repair, rest, refuel and rehydrate are the 4 P’s that are so important, not just for athletes with RED-S, but it applies to all athletes.

Big thanks to Aiveen Connolly (@aiveen_nutrition) for writing this blog.


  1. Mountjoy M, et al. 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. doi: 10.1136/bjsports-2014-093502. PMID: 24620037.

  2. Nattiv A et al. American College of Sports Medicine. American College of Sports Medicine position stand. The female athlete triad. Med Sci Sports Exerc. 2007 Oct;39(10):1867-82. doi: 10.1249/mss.0b013e318149f111. PMID: 17909417.

  3. Mountjoy M, Sundgot-Borgen JK, Burke LM, et al IOC consensus statement on relative energy deficiency in sport (RED-S): 2018 update British Journal of Sports Medicine 2018;52:687-697.


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