What Doesn't Kill Us: How Freezing Water, Extreme Altitude, and Environmental Conditioning Will Renew Our Lost Evolutionary Strength

by Scott Carney

Brown fat may be the missing organic structure that separates humans from the natural world. White fat stores caloric energy from food, which the body tends to burn only as a last resort. In fact, it’s difficult to burn the spare tire off your waistline because the body is programmed to store energy; even during intense exercise routines the body will completely deplete muscles of energy before it switches to white fat. Brown fat is different. Most people create it automatically when they’re in cold environments by way of a process called beiging. Essentially, the body detects physical extremes and starts to store mitochondria. When brown fat starts to work, the mitochondria suck white fat through the bloodstream and metabolize it directly to generate heat. Because most people do everything they can to avoid environmental extremes, they never build up brown fat at all. If we lived without clothing the way our distant ancestors must have, then we would have to rely on the internal properties of brown fat to keep us alive during the winter months and cold nights.