RED-S: What You Should Know

 Editors Note: At Gnarly we feel it is important to bring awareness to RED-S (formally referred to as the Female Athlete Triad) as it relates to the health and performance of athletes (including men). Readers must know we are not attempting to diagnose or treat any medical conditions in this article.


A few months ago we shared two articles authored by athlete Jasna Hodzic about her personal experience with RED-S. In Part I and II, she reveals her diagnosis story and how she manages this “relative energy deficiency syndrome” as part of her active lifestyle.

This syndrome is prevalent in sports that are impacted by strength:weight ratios, so we thought it’d be a good idea to add more context for all those interested in learning more.

Photo by Matt Burbach

What is this “RED-S” syndrome? Is it the same as the Female Athlete Triad? 

The International Olympic Committee points to the root of this diagnosis as an imbalance between energy intake and energy expenditure (Mountjoy, Et. Al, 2015).

Relative Energy Deficiency in Sport is the updated label for the “Female Athlete Triad.” Classifying this as “RED-S” opens up the diagnosis for male athletes and encompasses a wider range of symptoms beyond the trio of disordered eating, menstrual dysfunction, and low bone density.

When athletes burn more calories than they are consuming for an extended length of time, their physiology reacts by influencing metabolism, menstrual cycle, bone mineral density, immune system, protein synthesis, cardiovascular health, and influences the athletes’ health in the short term and long term (Ackerman, Et. Al, 2020).

Photo by Eliza Earl

How does this condition manifest? Why do athletes underfuel? 

Low energy availability happens both consciously and unconsciously in athletes. Even when athletes are not meaning to restrict calories, it can be difficult to keep up with the number of calories burned as training load increases. The imbalance between energy intake and expenditure can also happen when athletes think they are fueling enough, but their training puts immense strain on the bod, therefore creating a long-term caloric deficit.

The body has adaptive measures to postpone starvation, but this is where the symptoms of RED-S manifest. The equation for weight loss is to consume fewer calories than you burn, but this can cause long term health concerns if the athlete is depriving their body of essential nutrients while simultaneously still pushing it to perform.

Concepts like “power to weight ratio” and “racing weight” are what athletes often think will improve their performance or appearance based on social norms in sport. These misconceptions around weight loss can lead athletes to underfuel given the demands of their training, and ultimately put them at high risk for conditions like RED-S.

Misunderstanding weight loss and adequate sports nutrition contribute to the prevalence of RED-S among athletes and its inconspicuousness in the sports world (Long, 2020).

Photo by Austin Schmitz

What are the consequences of RED-S? Are there any performance implications? 

Athletes with low energy availability are more at risk for illness, fatigue, and deficiencies in their diet. This can pose problems with the musculoskeletal, endocrine, gastrointestinal, renal, and cardiovascular systems. Psychological impairments are also found to be common in this condition (Logue, Et. Al, 2018).

One specific RED-S study surveying 1,000 female athletes demonstrated participants with low energy availability were more likely to experience decreased training quality, impaired decision-making, less coordination, limited concentration, mood changes, depression, and impaired endurance performance. This study also found the low energy availability group was 1.5 times more likely to report declines in competition and training performance (Mathisen, Et. Al, 2020). 

Another study with only male endurance athletes presented survey results indicating only 20% of participants were optimizing their energy availability. There is convincing evidence from this study to support further research on RED-S in male athletes and develop energy availability parameters to better understand the manifestation of this issue in the male athlete population (Lane, Et. Al, 2019).

Photo by Drew Smith

If I feel like I have RED-S, who would be the best person to consult? 

The short answer is: this falls under a dietitian’s scope of practice. Assessing energy availability is a key role for a dietitian in a clinical sports nutrition setting. Awareness of this condition among all athletes needs to be spread to the medical field and the people who interact with athletes as support staff. Awareness will help all athletes prevent and resolve these issues so they can reach their full potential and fuel properly (Mountjoy, Et. Al, 2015).

Where can I find more information on how to fuel properly?

Here are a few online resources you can reference and a website for finding a dietitian near you!

Find an expert
How much protein should you eat per day?
Ditching the Diet … Stop “Dieting.” Just eat right.
Everyday Supplemental Nutrition


Works Cited

Ackerman, K., Stellingwerff, T., Elliott-Sale, K., Baltzell, A., Cain, M., Goucher, K., . . Mountjoy, M. (2020). #REDS (Relative Energy Deficiency in Sport): Time for a revolution in sports culture and systems to improve athlete health and performance. British Journal of Sports Medicine, 54(7), 369-370.

Lane, A. R., Hackney, A. C., Smith-Ryan, A., Kucera, K., Registar-Mihalik, J., & Ondrak, K. (2019). Prevalence of Low Energy Availability in Competitively Trained Male EnduranceAthletes. Medicina (Kaunas, Lithuania), 55(10), 665.

Logue, D., Madigan, S., Delahunt, M., Heinen, E., Mc Donnell, M., & Corish, S. (2018). Low Energy Availability in Athletes: A Review of Prevalence, Dietary Patterns, Physiological Health, and Sports Performance. Sports Medicine, 48(1), 73-96.

Long, J. (2020, June 26). Ep. 43: Friday flow: The paradox of weight loss for athletes. Retrieved June 29, 2020, from https://intheflownutrition.com/blog/weightloss

Mathisen, T., Heia, J., Raustøl, M., Sandeggen, M., Fjellestad, I., & Sundgot‐Borgen, J. (2020). Physical health and symptoms of relative energy deficiency in female fitness athletes. Scandinavian Journal of Medicine & Science in Sports, 30(1), 135-147.

Mountjoy, M., Sundgot-Borgen, J., Burke, L., Carter, S., Constantini, N., Lebrun, C., . . . Ackerman, K. (2015). The IOC relative energy deficiency in sport clinical assessment tool (RED-S CAT). British Journal of Sports Medicine, 49(21), 1354.


Lizzie Larkins

Lizzie Larkins

Lizzie Larkins is a recent graduate from the University of Vermont where she earned a Bachelor’s of Science in Nutrition and Food Science. She raced all four years on the UVM Nordic Ski Team and is now transitioning into a full-time ski coaching position. Lizzie is a coffee connoisseur, runner, backcountry skier, and type 2 fun enthusiast who thrives on gratitude and positivity!

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