When Athletes Stop Adapting: Recognizing Low Energy Availability Before It Becomes RED-S

Low energy availability (LEA) can quietly undermine an athlete’s ability to recover, adapt, and perform—even when training appears to be progressing as planned. This article examines how prolonged energy deficiency can develop into Relative Energy Deficiency in Sport (RED-S), affecting metabolic function, hormonal health, bone integrity, immunity, mood, and performance. Using the Adaptation Triangle of training stimulus, recovery, and energy availability, it explains why sufficient fuel is essential for translating hard work into physiological adaptation. It also provides coaches with practical guidance for recognizing warning signs, opening supportive conversations, creating a prevention-focused training culture, and referring athletes to qualified healthcare and nutrition professionals when appropriate.