Energy availability as an integrative framework: reinterpreting the energy balance and carbohydrate-insulin models in...

This review reinterprets the Energy Balance Model (EBM) and the Carbohydrate-Insulin Model (CIM) within athletic contexts and evaluates their explanatory relevance for low energy availability (LEA) and relative energy deficiency in sport (RED-S).

We conducted a structured conceptual review using a narrative synthesis approach. Literature searches were performed through January 2026 in PubMed, Web of Science, and SPORTDiscus, using terms related to EA, LEA, RED-S, EBM, CIM, and athlete metabolic, endocrine, and performance responses.

Reductions in EA consistently induce endocrine, metabolic, and performance disturbances, independent of body mass changes. EBM primarily accounts for long-term regulatory adaptations associated with cumulative energetic strain, whereas CIM provides mechanistic insights into short-term alterations in substrate partitioning and hormonal signaling. Across sports disciplines, LEA has emerged as a coordinated multisystem physiological adaptation rather than an isolated consequence of reduced energy intake.

LEA and RED-S are most coherently interpreted within an EA-centered framework that integrates long-term energy regulation and short-term metabolic dynamics. This integrative perspective provides a unified physiological basis for understanding the metabolic adaptation, performance regulation, and health outcomes of athletes.