A Chemical Hunger
I'm impressed with how well-written this argument is:
We don't really understand obesity and existing explanations fall short.
There's good reason to believe compounds in our food and water supply are to blame. Such an explanation would solve a lot of mysteries around obesity (like why case rates increased more quickly post 1980, why altitude is inversely correlated with obesity, and why a "cafeteria diet" leads to greater obesity, controlled for calories).
Lithium seems like a particularly compelling explanation, at least in part.
If you were to ask me what conspiracy theory I'm most likely to believe, I'd say that the lithium in our water and food supply causes large scale obesity in this country. Or that The Lab-Leak Hypothesis is correct.