allostatic load

If allostasis is the body bending to meet life's demands, allostatic load is the wear and tear that accumulates from bending too often or never fully straightening back. The same stress hormones that protect us in an emergency become a slow toll on the body when they are switched on too frequently, too long, or at the wrong times.

Allostatic load builds up through several patterns: stress responses that fire repeatedly, that fail to turn off after the threat passes, that do not adapt to a recurring stressor, or that are blunted and force other systems to overcompensate. Over years this can show up as elevated blood pressure, abdominal fat, insulin resistance, immune dysregulation, and changes in brain regions like the hippocampus. The extreme end is sometimes called allostatic overload.

Developed by Bruce McEwen and Eliot Stellar, the concept reframes chronic stress not as a single hormone gone wrong but as the cumulative cost of an adaptive system used beyond its sustainable range. It helps explain how persistent stress and social adversity translate, over a lifetime, into measurable disease risk.