A rebuttal to that piece:
https://www.lesswrong.com/posts/7iAABhWpcGeP5e6SB/it-s-proba...
Their thesis doesn't hinge entirely on lithium, but their sloppy work and responses to the rebuttal mean people should take their work with a huge grain of salt.
https://slimemoldtimemold.com/2021/07/07/a-chemical-hunger-p...
This series of blog posts goes through various theories (and myths) regarding obesity.