Rethinking Energy Availability from Conceptual Models to Applied Practice: A Narrative Review

Area of Science:

• Sports Science
• Exercise Physiology
• Nutritional Science

Background:

• Energy availability (EA) is the energy remaining after exercise energy expenditure (EEE).
• Chronic insufficient EA leads to low energy availability (LEA), a key factor in Relative Energy Deficiency in Sport (REDs).

Purpose of the Study:

• To explore the evolution of EA and LEA concepts.
• To summarize physiological evidence on LEA.
• To discuss challenges in assessing and applying EA/LEA in athletes.

Main Methods:

• Review of experimental and observational studies on LEA outcomes.
• Evaluation of screening questionnaires (LEAF-Q, LEAM-Q) for validity and applicability.
• Assessment of hormonal, metabolic, and behavioral indicators for LEA detection.

Main Results:

• LEA is linked to hormonal changes (thyroid, reproductive), reduced metabolic rate, lower bone density, and impaired recovery.
• Screening tools have variable accuracy; hormonal and metabolic biomarkers offer more direct detection.
• Accurate measurement of dietary intake, EEE, and body composition in real-world settings is challenging.

Conclusions:

• EA is vital for athlete health and performance, but assessment limitations hinder diagnosis.
• Improved measurement techniques and integrated monitoring are necessary for early LEA detection.
• Preventing REDs requires better identification strategies and individualized nutrition guidance.