UCP1

In one line: A "heater" protein in fat that burns energy as pure heat.

UCP1 sits in special "brown fat" and does something unusual: it lets your cellular power plants run without making usable energy, releasing the fuel as heat instead. This is how the body warms itself, and it's a way to burn calories.

Fat-burners like clenbuterol partly work by turning this heater up. The dangerous extreme is the banned chemical DNP, which forces this wasteful heat-burning everywhere at once — it melts fat but can literally cook you from the inside, and it kills people. A vivid lesson in how the same mechanism can be helpful or lethal by degree.