The uncoupler 2,4-dinitrophenol (DNP) was once prescribed as a weight-reducing drug. How could this agent, in principle, serve as a weight-reducing aid?

Uncoupling agents are no longer prescribed because deaths can occur following use. Why might the ingestion of uncouplers like DNP lead to death?

The principle of Dinitrophenol (DNP) as weight loss agent is that it is an uncoupler, by uncoupling oxidative phosphorylation preveting synthesis of ATP. In turn the body need for energy increases metabolism of fats releasing excess heat from the break down of adipose tissue and hence resulting in weight loss.

High intake of DNP or other uncouplers can collapse ATP synthesis and increase body temperature extremely resulting to hyperthermia which may lead to death.