Low fat diet advice is cascaded, not proven

The New York Times' review of Good Calories, Bad Calories put the current situation of bad advise well.  First they explained how cascades work:

But suppose, instead of the audience members voting silently in unison, they voted out loud one after another. And suppose the first person gets it wrong.

If the second person isn’t sure of the answer, he’s liable to go along with the first person’s guess. By then, even if the third person suspects another answer is right, she’s more liable to go along just because she assumes the first two together know more than she does. Thus begins an “informational cascade” as one person after another assumes that the rest can’t all be wrong.

And then they explain how these cascades are really common in science, especially medicine:

Cascades are especially common in medicine as doctors take their cues from others, leading them to overdiagnose some faddish ailments (called bandwagon diseases) and overprescribe certain treatments (like the tonsillectomies once popular for children). Unable to keep up with the volume of research, doctors look for guidance from an expert — or at least someone who sounds confident.

And that is how we ended up being told to eat a low fat diet!  Dr. Keys gave the original, unproven advice to eat low fat and the rest just followed or "cascaded" along.