Tracking changes in the body during fasting takes into account indicators of mental well-being and physiological parameters. The aim of the study was to measure psychological and physiological reactions, along with their mutual relations, caused by 8 days of water-only fasting. Fourteen men aged 35 to 60 participated in the study, divided into two groups, younger and elder. In addition to physiological parameters, psychological data were collected using four different tests. The obtained results confirmed reduction in body weight, systolic blood pressure, resting diastolic blood pressure and glucose level, and increase in resting heart rate, cortisol and β-hydroxybutyrate concentration. However, no significant psychological changes were observed under the influence of fasting intervention. A significant interaction effect occurred for the state anxiety variable determined before and after the fasting intervention for both groups. Moreover, negative correlations between physiological (cortisol) and psychological factors of subjectively assessed stress were revealed. The only effect on cognitive ability was seen when responding to simple tasks. The study confirmed the beneficial effect of 8 days of water-only fasting on physiological variables without affecting mental well-being. The relatively high level of well-being after fasting intervention was independent of the physiological indicators of stress.

Background/Objectives: Fasting and physical exertion positively affect body mass and composition. This study aimed to examine the effects of physical changes induced by eight days of water-only fasting and a physical exertion test and their influence on body satisfaction and body image parameters in middle-aged men. Methods: Fifteen participants were assessed for physical (height, body mass, and body composition) and psychological (body satisfaction, evaluation of body parts, and body image determinants) aspects before and after the fasting intervention, both at rest and post-exercise. Correlation and concordance coefficients were calculated for the analyzed variables. Results: It was found that the fasting intervention led to a reduction in body mass and a favorable shift in body composition, while also increasing satisfaction with one’s body and its specific parts. This positively impacted volunteers’ self-assessment of their health status. Selected body image parameters remained at an average level for the male population and did not change following the fasting. Attitudes toward body weight control methods and their perceived effectiveness did not change either. Participants favored reducing food intake and eliminating high-calorie products from their diet, rejecting the use pathological methods typically associated with eating disorders. A few associations between physical and psychological aspects of corporeality were observed, whereas significant correlations between satisfaction with body parts and parameters and a positive body image were confirmed. Conclusions: The above suggest that physical conditions and their changes resulting from fasting and physical exertion lead to a positive influence on body satisfaction and its components but do not alter body image.

Background/Objectives: Prolonged fasting induces substantial metabolic and neuroendocrine adaptations; however, less is known about the accompanying psychological changes. This study evaluated changes in subjective well-being and mood during an 8-day fast in relation to serum concentrations of α -endorphin, serotonin, oxytocin, and cortisol. Methods: Fifteen male subjects in good health completed an 8-day fast. Subjective well-being was assessed each day using a comparative self-rating scale, and mood was evaluated using the Polish version of the UWIST Mood Adjective Checklist (UMACL). Serum concentrations of α-endorphin, serotonin, oxytocin, and cortisol were measured before and after the fast, both at rest and following a maximal exercise test on an ergometer. Results: Subjective well-being gradually improved during the fasting period, and tense arousal, a dimension of mood, decreased. No significant changes were observed in energetic arousal or hedonic tone. The combination of fasting and exercise was associated with significant increases in α-endorphin, serotonin, and cortisol concentrations. Fasting was associated with a significant increase in post-exercise cortisol concentrations, whereas exercise after fasting was associated with a significant increase in serotonin concentrations. Despite concurrent psychological and hormonal adaptations, no consistent relationships were found between changes in hormone concentrations and psychological variables. Conclusions: Prolonged fasting was accompanied by gradual psychological adaptation, reflected in improved subjective well-being and reduced tension, whereas exercise under these conditions was associated with neurohormonal changes. These changes were associated with the coordinated activation of multiple neuroendocrine systems, suggesting that psychological and neuroendocrine adaptations represent complementary responses to prolonged metabolic stress rather than being opposing processes.