Relative Energy Deficiency in Sport (RED-S)

“The syndrome of RED-S refers to impaired physiological functioning caused by relative energy deficiency, and includes but is not limited to metabolic rate, menstrual function, bone health, immunity, protein synthesis, and cardiovascular health.”

Relative energy deficiency in sports (RED-S) is caused when energy intake from food is lower than the energy used for exercise. Low energy availability (LEA) describes this change in energy intake compared to exercise output. There is insufficient energy available for the body to complete exercise and normal functions for everyday life. Therefore, it can be very detrimental to overall health and performance. 


RED-S and LEA has been well documented in female athletes. However, current research suggests males are just as high risk. Both recreational and elite athletes are at risk of suffering from LEA due to numerous factors and it can be intentional or unintentional. This can include:

  • a desire to reduce body fat by reducing overall energy intake in the hope that this will improve performance.
  • changing body composition for aesthetic reasons where this may be desirable or due to small/revealing competition outfits (ballet, athletics and gymnastics).
  • high energy demands of the sport and the athlete not meeting these demands. For example: rowing, distance running or cycling.

Whether intentional or not, LEA can have severe consequences on health and performance. 

Common symptoms or side effects of RED-S include:

  • Altered menstrual cycle (amenorrhea) 
  • Fatigue or low energy 
  • Altered mood 
  • Poor concentration 
  • Failing to improve 
  • Under-performance 
  • Recurrent injuries 
  • Low mood and libido
  • Poor sleep quality  
  • Gastrointestinal problems 
  • Stress fractures and other overuse injuries 


The key to preventing RED-S is to ensure adequate energy intake through diet to support training needs. 

  • Ensure you have consistent meals and snacks that have adequate energy to support overall energy intake.
  • Avoid skipping meals or prolonged periods of time without eating. Always optimise pre-training/competition and post-training/competition food intake to help support energy availability and reduce the risk of RED-S.
  • Your energy intake needs to match your training load and requirements for that day. Training will change during an off-season period compared to pre-season and in-season. Even across a normal training week the duration and intensity will be different each day. Therefore, your food intake should change accordingly to match the change in energy output. 

A sports dietitian can help to ensure you are achieving sufficient energy from your diet to support your training load. If body composition changes are a goal, it is possible to achieve sufficient energy intake from training whilst still meeting body composition goals. This should be done under the guidance of a sports dietitian to prevent health and performance consequences. 


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