The third of Marshall's body-scholarship commitments: understand the *mechanism of action* of what you put in your body. "It's shocking how people drink coffee and don't understand caffeine's mechanism of action." His worked example is caffeine and adenosine: adenosine is the signal that makes you sleepy; caffeine, shaped like adenosine, blocks its receptors so you don't feel the tiredness that is still there. The body compensates by producing *more* adenosine — which is what "tolerance building" is, and why regular users need ever more caffeine just to reach baseline. (Full mechanism and strategic-usage patterns: [[Caffeine Mechanics - Adenosine and Strategic Usage]].) The point isn't caffeine specifically; it's that knowing the mechanism converts a blind habit into a tunable tool. Marshall's recommended on-ramps are deliberately gentle: Arvind Narayanan's "The Calculus of Caffeine Consumption," Examine.com's science summaries ("masterfully good"), Gwern.net (a thorough amateur who cites his sources), and LeanGains' Martin Berkhan on how food is processed and muscle is built. Intimidating at first, but "it's your body, after all — what could be more important to learn?" A caution this enables: beware the headline chain "X lowers Y; Y correlates with disease; therefore eat X." Mechanism-level understanding is what lets you catch such dangerous leaps (see [[Surface Analogy Fails to Predict Mechanistic Effects]]). --- *Source: [[Book Inventory/Progression|Progression]] (Sebastian Marshall, 2016) — Upstream Effects #3 — Chemica*