Relative Energy Deficiency in Sport (REDs) happens when an athlete’s body doesn’t get enough fuel to cover daily life and training combined. It’s easy to miss because it doesn’t look like one injury — it shows up as a cluster of problems across the body.
The core issue
When “energy availability” — what’s left over after training costs are subtracted from what you eat — stays too low for too long, the body deprioritizes reproductive hormones, bone building, and immune function. REDs isn’t just a female athlete issue either: it originally grew from the “Female Athlete Triad,” but the IOC’s current framework recognizes male athletes experience it too, with their own symptom pattern.
A key consequence: bone stress injuries
Bone is constantly rebuilt in response to load, a process that depends on adequate energy and normal hormones. Under sustained low energy availability, that rebuilding falls behind, bone density drops, and stress fractures become more likely. A recurring stress fracture with surprisingly little training behind it is one of the more common ways REDs gets picked up. See our dedicated guide on bone stress injuries for how these are graded, diagnosed, and rehabbed.
Other signs to watch for
- Missed or irregular periods (or reduced libido in men)
- Frequent illness, slow recovery
- Performance dropping despite harder training
- Persistent fatigue, low mood
There’s no single test for REDs — diagnosis comes from a structured assessment of symptoms, training, and eating patterns. Treatment usually means closing the energy gap, often with a physician, sports dietitian, and mental health professional working together. Adequate calcium and vitamin D intake support bone health but do not on their own fix an underlying energy deficit.
This page is educational and general in nature and does not replace an individualized evaluation — see our medical disclaimer. If you’re concerned about symptoms of an eating disorder, the National Alliance for Eating Disorders helpline can help you find support.