There's no shortage of weight-loss supplements claiming to "burn" fat, but one in particular, 2,4 dinitrophenol (DNP), might be taking the axiom to heart a little too literally.

Once widely available in the U.S., DNP was banned in 1938 due to severe side effects. And they are severe. In addition to cataracts and skin lesions, DNP can cause hyperthermia, which can kill you. Even if it doesn't kill you, DNP can leave you with severe brain damage.

Despite the dangers, it's been called the "king of fat-loss drugs" and is making a comeback in the healthy living community. A recent British study found a jump in inquires about DNP between 2012 and 2013, and a 2011 report from the U.S. National Institutes of Health indicates that DNP-related deaths worldwide are increasing.

It's hard to pinpoint exactly how many people are using DNP, writes Ian Musgraves in LiveScience. But the recent uptick in DNP-related deaths is concerning. Some experts say that when it comes to DNP, it's not a matter of simply finding the right dose; even small ones are potentially lethal.

"If I told you that in small doses, arsenic could also help you lose weight, would you do that?" says Michael Nusbaum, M.D., and founder of The Obesity Treatment Centers of New Jersey. "This is the same thing."

How does it work? Essentially, DNP makes the mitochondria in your cells less efficient at generating energy. You end up losing weight as the food you're eating is turned into "waste" heat rather than energy or fat, and if your body temperature rises enough, you'll literally cook from the inside out, according to Musgrave. Lovely.

Which brings us to the next question: If DNP is so dangerous, why is it available online? Sellers exploit a loophole: In most countries-including the U.S., U.K., and Australia-consumption of DNP is banned, but selling it is not (DNP is also used in chemical dyes and pesticides). Plus, people know that the weight-loss industry is a multi-billion dollar market, Nusbaum says. "There will always be someone who's willing to go out and make a buck off that."

DNP shouldn't even be a last resort for weight loss. If you're hoping to shed pounds, consider the myriad alternative methods. Even better? Check out these 22 expert-approved tips that really work.