Have you read anything from SMTM? Their work has been on HN a few times and they dive deep into the rabbit hole of what causes obesity. Fascinating stuff. https://slimemoldtimemold.com/
A series of mysteries as to different features of the obesity epidemic, that could possibly narrow down the causative factors. For example, people in higher elevations tend to be thinner than those in lower elevations, so perhaps the bad chemical is flowing downriver and accumulating at lower elevations.
