Review proposes tailoring exercise, heat exposure and calorie restriction to the body's capacity to recover

Review proposes tailoring exercise, heat exposure and calorie restriction to the body's capacity to recover

On September 10, physiologist Consuelo Borrás of the University of Valencia published a review on hormesis. She proposes assessing adaptive reserve, the body's capacity to withstand stress and recover from it. In her model, the same dose of exercise, heat exposure or calorie restriction can trigger a protective response in one person and overload another.

Hormesis is a two-phase response to stress: a low dose activates protective processes, while a higher dose causes harm. For a stressor to be beneficial, the body must detect the signal, activate its defenses, repair the resulting damage and return to a stable state. The outcome depends on both the dose and the body's capacity to complete this cycle.

Borrás calls this capacity adaptive reserve. It encompasses metabolism, the systems that keep proteins functioning, the immune response, tissue repair and DNA protection. Autophagy, the cellular recycling of damaged components and misfolded proteins, helps complete this process; the immune response resolves inflammation and supports tissue repair.

In experiments in fruit flies with an altered GCN2–ATF4 cellular stress response system, the outcome already depended on the tissue and the strength and duration of the signal. Borrás's review adds another factor: the body's baseline capacity to complete the stress response and recover.

Age, chronic diseases and past exposure to stress alter this reserve. Two people of the same age may respond differently to the same dose: moderate stress triggers repair in someone with greater reserve, while someone with less reserve reaches overload sooner. In Borrás's model, the aging body often retains the signal generated by stress, while its defense and repair systems function less effectively.

For future trials of interventions against aging, Borrás proposes comparing assessments of health and everyday functioning with molecular measures that indicate the body's condition, defining safety limits in advance and tracking how the range of tolerable stress doses changes over time. She also proposes analyzing data from women and men separately. This design would allow researchers to test whether baseline adaptive reserve changes a participant's response to a given dose.