Dinitrophenol (DNP) was an effective but dangerous weight loss drug in the 1930s, causing hyperthermia and death.

“this was dinitrophenol this was a substance that was used in the munition factories to make tnt so dinitro tnt a physician tainter in the 1930s basically said maybe this is good for weight loss actually introduced dinitrophenol as a weight loss drug it was available over the counter it wasn't a prescription so anyone could go like buying vitamins get some dnp for weight loss it actually worked so a lot of people hundreds of thousands of people took dinitropheno for weight loss and it worked”