Are You Fueling Enough? What Runners Need to Know About LEA & REDs
I just got back from The Running School New York- a running camp in the Catskils where I gave a lecture on Low Energy Availability (LEA) and Relative Energy Deficiency in Sport (REDs). After the lecture, I was blown away by how many athletes came up to talk with me. I spent more than an hour answering questions, and I know that many of those runners walked away wondering, “Could this be happening to me?”
This is the second time I have given this lecture at a running camp this summer (the first was at Wingfoot) and after both talks I left thinking: we need to talk about this more.
As a physical therapist who works with runners, I see athletes every week who are doing “everything right”—training consistently, strength training and working hard, but they keep getting injured, feel exhausted or simply stop responding to training. That is when we have to look deeper and ask ourselves is this becuase of training or something else?
LEA and REDs Are Related—but Not the Same Thing
Low Energy Availability occurs when the energy you take in from food isn't enough to support both your exercise and normal physiological functions. Your body still has to maintain your brain, bones, hormones, immune system, cardiovascular system and everything else keeping you alive. LEA is not one moment in time, it is a continuum from from adaptable to problematic.
REDs is the syndrome of impaired health and performance that can develop when an athlete is exposed to problematic LEA.
REDs affects both women AND men. [1] And this isn't rare. A recent systematic review found LEA in approximately 45% of athletes studied. Athletes with LEA demonstrated poorer running and endurance performance, training response, concentration, coordination, explosive power and agility. Bone health is particularly concerning, with LEA associated with impaired bone health and greater risk for bone stress injuries. [2]
A lot of times LEA doesn't happen on purpose. Many athletes don't even know how many calories they are supposed to consume during trianing. So if you are an athlete or parent that isn't sure, I always recommend seeing a sports dietitian at least a few times.
What Does REDs Look Like?
This is where things get a little tricky.
In women, the menstrual cycle gives us an important window into health and energy availability. Missing periods, increasingly irregular cycles or delayed menarche are not “normal for runners.”
Menstrual dysfunction combined with recurrent bone stress injuries, fatigue, declining performance or difficulty recovering should raise concern. [1,3]
Men can be harder to identify because we don't have that obvious monthly marker. Decreased libido, fewer morning erections, decreased testosterone or luteinizing hormone, recurrent injuries, poor recovery, fatigue and declining performance can all be clues. [1,2]
Bloodwork can provide additional pieces of the puzzle—but there is no single blood test that diagnoses REDs.
Depending on the athlete and clinical presentation, a sports medicine physician may consider bloodwork as part of a larger evaluation. The important point is that labs must be interpreted in context rather than treating one number as the entire problem.
This brings up two things I hear frequently: “My thyroid is low, so my thyroid must be the problem,” or “I'm tired, so it must just be my iron.”
True thyroid disease and iron deficiency absolutely exist and require appropriate medical evaluation. But REDs can also affect metabolic and endocrine function, including thyroid-related physiology, while nutritional deficiencies can coexist with inadequate energy availability. [1,3] One abnormal lab value doesn't necessarily explain the entire clinical picture.
REDs is a clinical diagnosis made by an appropriately trained physician—not a diagnosis made from ferritin, TSH or any other isolated number. So if you have been told you have a thyroid issue or iron issue and you have other signs and symptoms of LEA/REDS it is okay to get a second opinion - seek out a physician that understands LEA and REDS.
It's Not Just About Total Calories
When and what you eat can be just as important as total calories.
An athlete can consume a seemingly adequate amount of energy over 24 hours but spend large portions of the day in an energy deficit. Research examining within-day energy deficiency suggests that spending more time in significant energy deficit may be associated with endocrine and metabolic disturbances. [4]
In this world where protein in King (or Queen) Carbohydrates forgotten about. BUT for endurance athletes like runners they are key.
The current IOC consensus recognizes low carbohydrate availability as an emerging consideration in REDs, and carbohydrate availability may influence bone health independently of total energy availability. [1,3]
Translation for runners: regularly running fasted, avoiding carbohydrates or going long periods surrounding training without adequate fuel may matter—even if your total daily calories eventually “add up.”
Where Does Physical Therapy Fit?
As a PT, I don't diagnose REDs.
But I absolutely need to recognize it.
Sometimes a PT is the one who sees the athlete the most or has the strongest relationship with the athlete so it is very important we can recognize and refer out appropriately.
If a runner comes to me with their second or third bone stress injury, persistent injuries, poor recovery, declining performance or unexplained fatigue, I need to ask more questions rather than only focusing on the exercise.
Diagnosis belongs with the physician, and treatment should begin with an MD experienced in sports medicine and a sports dietitian. Depending on the athlete, the team may also include a PT, athletic trainer and mental-health professional. [1] This multidisciplinary approach is also how I teach REDs screening and management clinically.
My role as the physical therapist is to help manage the injury, appropriately modify training load, restore strength and rebuild running capacity while communicating with the medical and nutrition team.
Recognizing that something bigger may be going on—and making the right referral can make all the difference for an athlete.
If you want more information download the RUNsource app on apple or google - there is a nutrition section and MDs and dietitains talk about many of these things on the videos. It also has a lot more information and you can ask questions about it.
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References
Mountjoy M, Ackerman KE, Bailey DM, et al. 2023 International Olympic Committee's (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med. 2023/2024;57:1073-1098. doi:10.1136/bjsports-2023-106994.
Gallant TL, Ong LF, Wong L, et al. Low Energy Availability and Relative Energy Deficiency in Sport: A Systematic Review and Meta-analysis. Sports Med. Published online 2024. doi:10.1007/s40279-024-02130-0.
Heikura IA, McIntyre A, Kraus EA. Nutrition for Female Athlete Bone Health. Sports Science Exchange. 2023;36(241):1-7.
Logue DM, Madigan SM, Melin A, et al. Low Energy Availability in Athletes 2020: An Updated Narrative Review of Prevalence, Risk, Within-Day Energy Balance, Knowledge, and Impact on Sports Performance. Nutrients. 2020;12(3):835. doi:10.3390/nu12030835.
Lodge MT, Cirella SM, Hartman ME, Logan NE, Ward-Ritacco CL. Risk of Low Energy Availability, Disordered Eating, Eating Disorders, and Bone Stress Injuries in United States Female Track and Field. Journal of Exercise and Nutrition. 2025;8(1):7.
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