Chewing as a Brainstem-Mediated Stress Modulator: An Evolutionary Hypothesis Linking Orofacial Neural Activation to Emotional Eating and Obesity

Although emotional eating is a well-documented contributor to obesity, the neurological basis for

stress-induced chewing remains largely under-explored. This paper proposes a novel hypothesis: that

chewing functions as an evolutionarily conserved mechanism to initiate parasympathetic

modulation during stress recovery, mediated via cranial nerves, including the trigeminal (V),

glossopharyngeal (IX), and hypoglossal (XII) that converge in the brainstem.

The act of chewing may serve as a neurosensory signal initiating the shift of autonomic tone

from sympathetic arousal toward parasympathetic regulation. In ancestral environments, such

orofacial activity may have played a subtle but adaptive role in recovery from acute stress. In

modern contexts, this biological mechanism is activated not by survival behaviors, but by highly

palatable, ultra-processed foods that simultaneously engage reward circuitry. The result is a

mismatch: stress triggers an innate drive to chew, which modern food environments exploit,

reinforcing patterns of compulsive eating and contributing to the obesity epidemic.

This hypothesis integrates neuroanatomical, behavioral, and evolutionary perspectives,

emphasizing chewing as a transitional regulator rather than a direct inhibitor of stress. Future

research should investigate the timing, pathways, and limits of this mechanism using

neuroimaging, heart rate variability, and endocrine markers to assess how orofacial activity

influences the stress-recovery process.