Why energy availability matters for athletes
Unlike a simple calorie deficit, EA specifically relates remaining energy to the metabolically active mass (fat-free mass, FFM) that must be fuelled. An athlete with more muscle mass needs more energy at a given EA level. The IOC and sports medicine organisations use 45 kcal/kg FFM/day as the threshold for adequate EA, below which physiological systems begin to be compromised.
Low EA is common in athletes — particularly in weight-sensitive sports, endurance sports, and among female athletes — and can develop unintentionally from high training volumes without proportionate increases in food intake. The long-term consequences include stress fractures, hormonal suppression, impaired recovery, and increased injury risk.