I would love to see an RCT on a ton of really common environmental contaminants at different dosages in the human diet. Of course this would be incredibly unethical and inefficient with respect to human welfare, but it would, I think, finally get people to believe that there are obesegenic compounds (and viruses) that need to be avoided for proper metabolic health.

Phthalates, Adenovirus 36, bisphenols, certain pesticides and fungicides--which ones should we be investing in getting rid of?