I read a really interesting series of articles recently that posited (with graphs!) that there may be a chemical component to obesity that is down to industrial processing introducing additional chemicals to our foodstuffs (one of the suggestions is lithium from lithium grease for example).
My problem is that I don't know enough about the science to figure out whether or not the argument is actually any good, or if it's one of those 'this all totally seems logical when you read it but if you do any follow up work around it the whole thing will fall apart' things. The series starts here, for anyone who's interested, but YMMV and it may be total garbage: https://slimemoldtimemold.com/2021/07/07/a-chemical-hunger-part-i-mysteries/