Its been a while but I think dnp is dinitrophenol. I am sure the spelling is wrong.
I seem to remember the way they figured out it would cause fat loss was in the early 20th century workers in munitions plants were losing fat and they figured out it was dinitrophenol in the air and getting on the skin. I think dnp was available as a wt loss drug easily available for a while back then.
I might be wrong though as I have not used dnp since mid 90s so its been 20 yrs since I researched it