Chapter 4: Stress, Metabolism, and Liquidating Your Assets

Under normal conditions, the body efficiently stores nutrients from meals as glycogen, triglycerides, and proteins through insulin-mediated anabolic pathways, prioritizing long-term energy reserves. When stress is activated, however, this metabolic strategy reverses completely. The sympathetic nervous system and hypothalamic-pituitary-adrenal axis suppress insulin secretion while elevating glucagon, glucocorticoids, epinephrine, and norepinephrine, triggering simultaneous breakdown of stored fuels. Glycogenolysis releases glucose directly into circulation, lipolysis converts triglycerides into free fatty acids and glycerol, and proteolysis liberates amino acids that hepatic gluconeogenesis converts to additional glucose. This coordinated mobilization floods the bloodstream with metabolic substrates capable of sustaining intense physical exertion during fight-or-flight responses. While acute stress activation represents an elegant adaptive mechanism essential for survival, chronic psychological stress creates severe metabolic dysfunction. Repeated cycles of energy mobilization and storage depletion induce profound fatigue and inefficiency. Extended protein catabolism produces muscle wasting and glucocorticoid-induced myopathy, progressively weakening skeletal musculature. Persistent elevation of circulating glucose and fatty acids overwhelms cellular insulin sensitivity, establishing insulin resistance and precipitating type 2 diabetes mellitus. Glucocorticoid-mediated suppression of insulin receptor responsiveness in adipose tissue can trigger medication-induced steroid diabetes in susceptible individuals. The metabolic consequences extend beyond glucose dysregulation; chronic hyperglycemia damages renal filtration capacity, accelerates atherosclerotic plaque formation in arterial endothelium, induces protein glycation in ocular lens tissues causing cataracts, and promotes systemic aging. Sapolsky illustrates how stress physiology demonstrates the fundamental paradox of adaptation: mechanisms that preserve life during acute emergencies become pathogenic when chronically activated, transforming survival into vulnerability.