What is RED-S and why do we care about it?

While we all know that sport and exercise is good for us, in some situations it can have a negative impact on health and performance. This can occur when too few calories are consumed. Insufficient calorie intake can result in a state of low energy availability. Low energy availability causes the body to go into energy saving mode as there are too few calories left over for the body after accounting for the calories expended through exercise. Low energy availability can lead to the syndrome of relative energy deficiency in sport (RED-S). RED-S is a set of symptoms that has various health and performance implications.

Hormonal pathways become dampened in athletes with RED-S. This can result in missing periods, a down regulated metabolism, and poor bone health. RED-S also has negative implications for the cardiovascular system, gastrointestinal function, the immune system and many more physiological processes. RED-S also has negative implications for performance. This may occur directly or cause athletes to miss out on training due to the increased risk of injury and illness.

RED-S can be the result of a clinical eating disorder, disordered eating or by a well intentioned change in nutrition in an attempt to improve performance. Sometimes RED-S also occurs unintentionally as many athletes are simply unaware of how many calories they need.

What to look for:


  • Missing or irregular periods in females
  • Low sex drive and decline in morning erectile function in males
  • Changes in weight or lack of expected growth and development in adolescent athletes
  • Recurring injuries and illness
  • Reduced body temperature and increased sensitivity to cold
  • Gastrointestinal issues such as constipation or bloating
  • Downy growth of hair on the body


  • Restrictive eating such as cutting out food groups, counting, measuring, or weighing foods
  • Avoiding food-related social activities
  • Secretive behaviour regarding food intake and/or exercise
  • Pre-occupation with food, calories, body shape, and weight
  • Additional training above what is required and/or difficulties taking rest days
  • Disturbed sleep and sleeping difficulties


  • Becoming withdrawn and reclusive
  • Anxiety, irritability, and difficulties concentrating
  • Increased attention and/or criticism of body
  • Body image dissatisfaction and distortion

It is very important to note that it should never be assumed that an athlete is fine just because they appear to be at a healthy weight, or even if they are overweight. Athletes may be in an energy deficit despite having a stable body weight due to reductions in resting metabolic rate. RED-S can occur in athletes of any sport, across any age, body size, culture, socioeconomic status, and athletic ability.

What to do:

Early identification and treatment is important to prevent the long-term health outcomes of RED-S. While addressing the underlying energy deficit is necessary, treatment of RED-S usually involves more than an athlete simply increasing energy intake and decreasing exercise energy expenditure. Like the treatment strategies employed, the time for recovery will differ with each athlete and their unique situation.

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