How to dismantle modern stressors: does a short trip to simulated Paleolithic conditions in the wild reduce cortisol levels? [version 1; peer review: 2 not approved]

Background: Chronic stress has become a central problem of our modern society. It appears plausible that our Paleolithic ancestors were more exposed to acutely life-threatening stress stimuli than chronically enduring psychosocial stressors. The aim of this study was to test whether it is possible to reduce physiological and psychological stress parameters by returning to simulated Paleolithic lifestyle conditions. Methods: In total, 15 volunteers undertook a four-day hiking tour simulating hunter-gatherer lifestyle conditions in a National Park. Saliva samples were taken at 5, 6 and 7 pm prior to, during and after the intervention and evaluated for cortisol concentration. Perceived stress was measured by the Perceived Stress Questionnaire. Results: The study was completed by 11 of the subjects. Mean body weight and fat mass decreased significantly during the intervention by 2.3 and 2.2 kg, respectively. There was a marked increase in cortisol levels on the first day of the intervention compared to baseline with a gradual return to baseline levels on the subsequent days. Individual cortisol responses were heterogeneous; in threes subjects, cortisol concentrations generally decreased from 5 to 7 pm, while in four subjects the opposite trend was observed. Conclusions: During this four-day outdoor intervention under simulated Paleolithic conditions, significant changes occurred almost exclusively at the first day of the study. The increase in cortisol levels at this point supports the hypothesis that some individuals respond by an increased release of cortisol as a result of adaptation to new environmental conditions.