Hormesis

Hormesis is a well-established biological principle: low to moderate doses of a stressor can produce beneficial adaptive responses, even when high doses of the same stressor would be harmful.

Familiar examples: exercise (muscle damage triggers stronger rebuilding), fasting (cellular stress triggers autophagy), cold exposure (cold stress triggers brown fat activation and autonomic training), heat exposure (heat shock proteins, cardiovascular adaptation), sun exposure (vitamin D, mood, with overdose causing skin damage).

Hormesis is the theoretical basis for nearly every "deliberate stress" practice in modern wellness culture — cold plunges, sauna, fasting, intense interval training. The mechanism is real. The dose matters.