The world is full of pseudoscientific fad diets, but the latest fad isn't just a diet — instead, it's a craze for lowering body temperature to "burn fat." The Atlantic looks at people who buy special ice vests, or take shirtless walks in winter, in the hope of losing weight.

Top image: Polar Bear Dip, Houghton Lake, MI, photographed by Joe Ross

In a nutshell, the theory is that exercise doesn't matter nearly as much as body temperature. Our bodies evolved to deal with two challenges, getting enough calories and staying warm, and now that we're warm all the time, our bodies never burn off the excess fat. We're suffering from "chronic overnutrition and chronic warmth," and our bodies are preparing for a winter that never arrives.

Bear in mind that there's very little clinical evidence for this notion, and no studies that prove its effectiveness — so people may be freezing themselves for nothing. Learn more over at The Atlantic.