For, Then Against, High-Saturated-Fat Diets

A steelman-then-rebut nutrition deep-dive. Part I: the puzzle (1800s Americans ate more bread with ~1% obesity; the China/France paradoxes) and the nutrition-blogosphere theory (Brad Marshall's Croissant Diet, Hyperlipid, r/SaturatedFat) that the ~1950 switch from saturated fat to omega-6 vegetable oils caused the obesity epidemic, via an omega-6:omega-3 inflammation imbalance or a Krebs-cycle/reactive-oxygen-species satiety mechanism (saturated fat signals fullness, PUFA doesn't). Part II: the direct evidence is against it — the diet mostly doesn't work (incl. his own and r/SaturatedFat self-reports), mouse studies show no clear trend, the huge sat-vs-unsat literature shows no strong protective-against-weight effect, and croissants are actually the least satiating food. Part III: the tension — there IS a dramatic obesity difference vs the past, but the efficient market of biohackers would have found a simple fix; three escape hatches (conventional CICO + food-reward à la Guyenet; non-diet causes like plastics/microbiome; or a set-point ratchet that bad diets raise but good diets don't lower). Ends more confused than he started.

Quality 74 · Strong. Strong, upper. A comprehensive, numerate, scrupulously even-handed deep-dive that steelmans the saturated-fat theory then dismantles it on the direct evidence, with sharp framing (figure out what Great-Grandpa did, not cavemen; the efficient-market-of-diets argument; the three escape hatches). Held at top-Strong by the bounded single-controversy scope and the deliberately inconclusive ending ('ending this research more confused than when I started').

Claude’s paradigm shift 50 · Moderate. Moderate (50). Reviews and rebuts pre-existing hypotheses (the PUFA theory is the blogosphere's, the food-reward model Guyenet's); the fresh contributions are the framing and the set-point-ratchet escape hatch, not a new theory.

Real-world impact 2 · Minor. Minor (2). An influential-within-discourse early careful treatment of the seed-oil/PUFA debate with a practical takeaway (avoid soybean/corn/safflower oil as a 'processed' proxy); no material-world change.