EA = (energy intake − exercise energy expenditure) / fat-free mass. A 65kg cyclist with 55kg FFM consuming 2800 kcal/day and burning 1000 kcal in training has an EA of (2800 − 1000) / 55 = 33 kcal/kg FFM — just above the clinical threshold. Below 30 triggers hormonal disruption, immune suppression, and stress-fracture risk. EA is a more meaningful number than total calories because it accounts for training load and body composition.