The fat we typically think of as body fat is called white fat. But there’s another type—known as brown fat—that does more than just store fat. It burns fat. Scientists used to think that brown fat disappeared after infancy, but recent advances in imaging technology led to its rediscovery in adult humans. Because brown fat is so full of blood vessels and mitochondria—that’s what makes it brown—it’s very good at converting calories into energy, a process that malfunctions in obesity.

In a study published October 5 in Cell Metabolism, Sanford-Burnham researchers discovered that orexin, a hormone produced in the brain, activates calorie-burning brown fat in mice. Orexin deficiency is associated with obesity, suggesting that orexin supplementation could provide a new therapeutic approach for the treatment of obesity and other metabolic disorders. Most current weight loss drugs are aimed at reducing a person’s appetite. An orexin-based therapy would represent a new class of fat-fighting drugs—one that focuses on peripheral fat-burning tissue rather than the brain’s appetite control center.

“Our study provides a possible reason why some people are overweight or obese despite the fact that they don’t overeat—they might lack the orexin necessary to activate brown fat and increase energy expenditure,” explains Dr. Devanjan Sikder, senior author of the study and assistant professor in Sanford-Burnham’s Diabetes and Obesity Research Center, located in Orlando’s Medical City at Lake Nona.

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