allostasis

Allostasis is the process by which the body achieves stability through change, adapting regulatory set points in response to challenges. Unlike homeostasis, which aims to keep variables within fixed ranges, allostasis emphasizes dynamic regulation and predictive adjustments coordinated by the brain across physiological systems, including the neuroendocrine and autonomic networks, to meet anticipated demands (e.g., energy, threat, or social signals).

Allostatic load refers to the cumulative burden on body systems from repeated or chronic activation of these adaptive responses. It arises when regulatory adjustments become overused or misaligned with actual needs. Researchers measure allostatic load using biomarkers from multiple systems, such as cortisol, catecholamines, inflammatory markers, blood pressure, and metabolic indicators, aggregated into an index. High allostatic load is associated with increased risk of cardiovascular disease, metabolic syndrome, cognitive decline, and mood disorders.

The concept, introduced by Sterling and Eyer in 1988, provides a framework for understanding how chronic stress and adverse conditions can shift physiological regulation and contribute to disease over time. Critics note definitional vagueness and measurement challenges, and some emphasize that adaptive changes can be beneficial in certain contexts. Nonetheless, allostasis remains influential in physiology, psychology, and aging research as a way to link stress, regulation, and health outcomes.