What is RED-S? 

Published by ABT Staff on

RED-S is a state of chronic low energy availability where how much energy an athlete needs does not match up with what the athlete is taking in. It comes from overtraining, underfueling, or both. 

According to Dr. Nicky Keay, it is a “clinical syndrome describing adverse consequences in terms of health and performance due to sustained lower energy availability (‘LEA’).”  LEA is where “there is a mismatch between energy intake and the combined energy demand from exercise and resting metabolic rate.”  

RED-S stands for “RED-S refers to Relative Energy Deficiency in Sport.”  You also might recognize it by another related name- the “Female Athlete Triad” (although technically, they are not the same thing). 

Recent years have seen increased education and awareness about RED-S, but studies suggest it is still shockingly common and underestimated.

RED-S, athlete struggling after a workout.

Symptoms of RED-S. 

RED-S can be characterized by physical and psychological symptoms. Many of these symptoms are minor in isolation. When taken together, they can indicate a bigger problem. 

Physical symptoms can include unexplained fatigue and low energy, performance decline, missing or irregular periods, digestive issues (bloating, discomfort, IBS), low libido, trouble staying warm, hair loss, and recurrent or persistent injuries or illness. 

Psychological symptoms can include anxiety around food, exercising, and rest, body dissatisfaction, increased irritability, depression, and poor concentration. 

Short Term vs. Long Term. 

One of the major problems with RED-S is that it sometimes results in short-term gains, which reinforces the behaviors that resulted in RED-S   But over time, the toll it takes on an athlete’s body catches up with them- both in sport and in life. 

Left untreated, it can impair systems throughout the body, including reproductive health, bone health, immunity, metabolism, heart health, and psychological health. One of the most concerning long-term impacts of RED-S (particularly for young female athletes) is low bone density, which can lead to an ongoing risk of stress fractures and osteoporosis well into adulthood. 

RED-S Is not the Same as An Eating Disorder. 

It is important to keep in mind that RED-S is not the same as an eating disorder or even disordered eating. They can coexist or overlap but do not have to be. 

Someone could have RED-S without significant weight loss. RED-S can also result from overtraining alone.

Athletes can fall into LEA or RED-S by accident- that is, they just do not realize how much they need to consume or simply are not hungry. 


A physician (usually a specific sports medicine doctor) can diagnose RED-S using blood tests, symptoms, and an assessment of your training/nutrition. 

There is not one definitive test that can tell you if you have RED-S. Here at Athlete Blood Test, if we observe blood biomarker levels—or a combination of blood biomarker levels and questionnaire responses—that suggest that someone may be struggling with either LEA or RED-S, we will recommend that you reach out to a medical professional to discuss your results and symptoms. 

Not every medical professional knows about and is trained in recognizing and treating RED-S. We strongly recommend working with a sports medicine doctor with specific expertise and experience in RED-S. We also recommend you work with a Registered Dietitian to make sure your calorie intake is sufficient to match your energy output. But it is important to rule out other medical conditions that may be causing similar symptoms first. 

Men and RED-S.

Men can get RED-S too. While the health impacts of RED-S on men are less established, it is clear that RED-S affects men as well. In fact, a number of researchers and writers theorize that RED-S in men is more underreported than in women. 

Who Is Most at Risk For RED-S? 

RED-S can impact anyone. That said, according to Project RED-S, endurance athletes (those with a high training load) and sports that promote a low body weight for aesthetics or performance (for example, long-distance running, climbing, gymnastics, rowing, and cycling) pose the greatest risk. 

Can You Recover from RED-S? 

Yes! As Project RED-S says: “With the right nutrition, mindset, and support, reversing most of the effects of chronic low energy availability should be possible.”  

Great Sources of Information on RED-S: 

Dr. Nicky Keay, Different Facets of the Same Underlying Imbalances in Athlete Behaviors, located here

The entire website for Project RED-S 

SportReady’s “Working With High-Performing Female Athletes” course.  

RED-S: The condition all runners need to know about,” by Emma Donnery and Jenny Bozon, Runner’s World, May 30, 2023.  

Boston Children’s Hospital, including the Female Athlete Program.

Some personal stories of RED-S and recovery:

Kelly Catale’s (@kelly.catale) story of her journey to finding food and a positive body image: 

Mary Cain’s (@runmarycain of @atalantanyc) article “I Was the Fastest Girl in America, Until I Joined Nike”

Doug Bentall’s writing on RED-S in middle-aged men. 

Jake Riley’s experience, as detailed in Runner’s World

Thoughts on Keeping Training and Nutrition Healthy and Balanced Generally: 

Pat McCurry of Idaho Afoot’s articles on Person Athlete RunnerThe Overvalued vs. The Undervalued, and What Exactly Is It That I Do.

Lauren Fleshman’s book “Good for A Girl