Relative energy deficiency in sport (RED-S)
Relative energy deficiency in sport (RED-S) is a condition that occurs when an athlete’s energy intake is insufficient to meet the demands of their training and daily activity. It affects both men and women and can have wide-ranging consequences for physical health, performance, and overall wellbeing. Recognising RED-S early is crucial to prevent long-term complications.
What causes RED-S?
RED-S arises when the calories consumed through food don’t adequately support the energy expended during exercise and basic bodily functions. This energy deficit can be intentional, such as through restrictive dieting, or unintentional due to increased training demands. The condition is associated with hormonal disturbances, impaired bone health, reduced immunity, and decreased metabolic function.
Athletes at risk include those in sports emphasising leanness or low body weight, endurance disciplines, or sports with aesthetic demands, such as gymnastics, dance, long-distance running, and cycling. Both young athletes and adults can be affected, and male athletes may also experience consequences despite often being under-recognised.
Signs and symptoms to watch for
RED-S can affect multiple body systems, and symptoms vary depending on severity and duration. Common signs include:
- unexplained fatigue or decreased performance
- disrupted menstrual cycles in women (including absent periods)
- low testosterone or reduced libido in men
- frequent injuries or stress fractures
- recurrent illness or slow recovery
- poor concentration and mood changes
- unintended weight loss or low body fat
Because symptoms can be subtle, athletes and parents may not immediately recognise RED-S, making awareness vital.
Steps to take if you suspect RED-S
If you suspect you may have RED-S, early action is essential. One section only includes a list:
- monitor energy intake and training demands to assess for a persistent imbalance
- reduce excessive exercise intensity or volume while maintaining nutrition
- keep a diary of symptoms such as fatigue, menstrual changes, injuries, or illness
- seek advice from a healthcare professional specialising in sports medicine, endocrinology, or nutrition
A multidisciplinary approach is often needed, involving a doctor, dietitian, and sometimes a psychologist or physiotherapist, to ensure safe recovery and performance management.
When to see a doctor
Prompt medical evaluation is recommended if you notice any of the following:
- missed periods for women or hormonal changes in men
- unexplained fatigue or declining performance
- repeated injuries or stress fractures
- weight loss despite adequate effort to maintain body mass
A doctor can perform investigations such as hormone tests, bone density scans, and metabolic assessments to confirm the diagnosis and guide treatment.
Management of RED-S
Treatment focuses on restoring energy balance, which may involve increasing calorie intake, adjusting training schedules, and addressing any nutritional deficiencies. Medical monitoring is essential to ensure hormonal and bone health recover. In some cases, treatment may require a gradual reduction in training load or temporary modification of competition schedules.
With early recognition and appropriate management, athletes with RED-S can regain performance, protect long-term health, and reduce the risk of complications such as infertility, osteoporosis, or chronic fatigue. Awareness, self-monitoring, and timely professional support are key to addressing this condition effectively.