Energy balance

Low energy availability (EA), defined as inadequate energy intake relative to exercise energy expenditure, is the primary trigger for Relative Energy Deficiency in Sport (RED-S), leading to compromised physiological processes including menstrual dysfunction, bone stress injuries, and impaired sports performance.

If you are an athlete training hard, you must eat enough to cover your exercise energy expenditure plus your body's basic needs. If you consistently eat less than this, you risk menstrual dysfunction, bone stress injuries, and lower performance. Do not rely on feeling 'fine'; use validated screening tools like the LEAF-Q if you are female, and consult a sports dietitian to ensure your energy intake matches your training load.