What relative energy deficiency in sport describes
RED-S describes a state where an athlete chronically takes in less energy than training and basic function require, leaving too little energy available for normal physiological processes. The underlying driver is low energy availability, whether from intentional restriction, disordered eating, or simply under-fueling a heavy training load.
It is broader than the older female athlete triad. While menstrual disruption and reduced bone density are central concerns in female athletes, RED-S also affects immune function, metabolism, mood, and performance, and it can affect athletes of any sex.
Recognizing low-energy-availability flags
Warning signs include loss or irregularity of menstruation, recurrent stress fractures or low bone density, frequent illness, persistent fatigue, and stalled performance. These flags signal that the body is conserving energy by downregulating systems it treats as nonessential.
This is general educational information, not medical advice, and RED-S is a serious clinical condition. Anyone showing these signs should seek assessment from a qualified medical professional rather than attempting to self-manage through diet changes alone.