Intermittent Fasting and Emotional Regulation: A Psychobiological Framework Integrating Metabolic, Neuroendocrine, and Interoceptive Mechanisms

Background/Objectives: Intermittent fasting (IF) has been widely investigated for its metabolic effects, including improvements in insulin sensitivity, lipid metabolism, and inflammatory markers. However, its psychological and experiential dimensions remain comparatively underexplored. The present narrative review examines IF within a psychobiological framework, integrating evidence from metabolic science, neuroendocrinology, and affective neuroscience to explore its potential impact on emotional regulation and interoceptive processes. Methods: A structured narrative literature search was conducted across PubMed, Scopus, and Google Scholar, focusing on studies published between 2000 and 2025. Eligible studies included human and relevant animal research addressing metabolic, hormonal, interoceptive, and psychological responses to IF. Evidence was synthesized thematically to identify convergent mechanisms linking metabolic adaptations to emotional and regulatory outcomes. Results: The available literature indicates that IF induces a metabolic shift toward lipid utilization, characterized by increased lipolysis, elevated circulating free fatty acids, and enhanced ketone body production, particularly β-hydroxybutyrate. These metabolic changes are accompanied by modulation of neuroendocrine pathways, including transient activation followed by adaptive recalibration of the hypothalamic–pituitary–adrenal axis, as well as alterations in insulin, leptin, and ghrelin signaling. Emerging evidence suggests that these physiological adaptations may influence central nervous system functioning through mechanisms involving neuroinflammation, mitochondrial efficiency, and synaptic plasticity. At the psychological level, IF appears to modulate interoceptive signaling, with heterogeneous emotional outcomes: structured fasting protocols have been associated with modest improvements in depressive symptoms and perceived stress in metabolically healthy individuals, whereas increased irritability, anxiety, or behavioral rigidity may occur in the presence of psychological vulnerability. Individual variability appears to be associated with differences in interoceptive sensitivity, stress reactivity, and traits related to anxiety, perfectionism, and eating-related pathology. Conclusions: Overall, IF may be conceptualized as a context-dependent psychobiological stressor whose effects extend beyond metabolic regulation to include interoceptive and emotional processes. These effects appear bidirectional, potentially promoting psychological resilience in some individuals while increasing the risk of affective destabilization or maladaptive behaviors in others. Current evidence remains limited by a lack of integrative and longitudinal studies combining metabolic and psychological measures. Future research adopting multidisciplinary approaches is needed to clarify the mechanisms underlying individual variability and to better define the potential benefits and risks of IF in both clinical and non-clinical populations.