The Thrifty Gut: Irritable Bowel Syndrome as an Algorithmic Mismatch of Evolutionary Energy Management

Background: Irritable Bowel Syndrome (IBS) remains a diagnosis of exclusion with no consensus on its ultimate evolutionary cause. Current treatments focus on symptom suppression rather than correcting the underlying regulatory logic. Hypothesis: This paper proposes the Thrifty Gut Hypothesis, a theoretical framework reframing IBS not as a defect, but as a manifestation of evolved energy management control policies driven by the "Selfish Brain." Moving beyond proximate pathological descriptions, I suggest that IBS phenotypes represent prioritized resource allocation strategies: IBS-C (constipation) minimizes metabolic variance via adaptive stasis, while IBS-D (diarrhea) represents a defense-biased regulatory response. Implications: By synthesizing data from postprandial hemodynamics and predictive processing, I posit that IBS represents a heuristic mismatch—where ancient regulatory biases optimized for scarcity and stochasticity become maladaptive in modern abundance. Crucially, this framework suggests that "hijacking" the vagal baroreflex via mechanical interventions could reset these priors.