Lol I see now that there is another thread only 30 minutes old talking about obesity stuff. This essay is about a history of fad diets, and IMO the most fascinating hypothesis about what is driving the obesity epidemic yet.

Yes I'm aware of the Slime Mold Time Mold arguments, "Calories in Calories out", and the Scott Alexander essay arguing for and against saturated fat diets. I still think this is very plausible and very interesting.

TLDR: American consumption of linoleic acid (omega 6) has skyrocketed since the 1960s. Other animals in our family tree enter into a state called "torpor" to prepare for hibernation, and they do this by increasing their intake of linoleic acid which signals their fat cells to begin storage. Squirrels, famously, switch to a diet high in acorns (high in Ω-6) as the winter approaches, which tells their bodies to start packing on weight in preparation for hibernation.

Squirrels need 8% of their calories to come from linoleic acid to switch into torpor, americans began to eat more than 8% of their calories in linoleic acid almost exactly when the obesity epidemic started.

human temperatures have also dropped by 1 degree fahrenheit since before the obesity crisis started and nobody knows why. Torpor is a plausible explaination