Obesity is an omnipresent threat to America’s health and future, but a possible solution may be on its way thanks to the discovery of a switch that turns on the body’s most masterful fat-burning machine — brown fat. Researchers from Harvard Medical School figured out how to burn fat from repurposing a bladder medication and published their findings in the journal Cell Metabolism.

Once researchers realized the FDA-approved drug mirabegron, typically used to treat overactive bladder, could boost brown fat’s metabolic burning efforts inside the body, they began trials. The drug was able to activate a receptor that lies on the surface of brown and white-yellow fat and bladder. If mirabegron was able to target and control the bladder’s beta-3-adrenergic receptor, researchers thought it might also be able to control fat and ultimately people’s weight. They guessed right.

Locating The Fat Fighter's 'On' Switch

There are two different types of fat in the body: brown and white-yellow. Brown fat is the good stuff and has the ability to metabolize efficiently by burning fat and calories while generating heat. The enemy is the white-yellow fat you can find stuck around your gut. It coats our vital organs and controls a slew of hormones, including hunger-appetite regulators.

Researchers gave 200 milligrams (mg) of mirabegron to 12 healthy men enrolled in the study. Immediately their brown fat had higher metabolic activity. It increased the average man’s metabolic resting rate by 203 calories per day, which is basically the number of calories you’d burn if you stayed in bed all day. The FDA only approved the drug for overactive bladders at a 50mg dosage, but participants tolerated it well.

"Brown adipose tissue, or brown fat, produces beta-3-adrenergic receptor at levels higher than nearly every other organ in the body," the study’s lead author Dr. Aaron Cypess, from National Institute of Diabetes and Digestive and Kidney Diseases, said in a press release.  "We showed that a one-time dose of the drug mirabegron stimulates human brown adipose tissue so that it consumes glucose and burns calories."

Because the beta-3-adrenergic receptor is shared by brown fat and the bladder, activating it would mean revving up the brown fat to burn more than it normally would in obese people. Conversely, people who are younger and in shape have higher levels of brown fat. When a person exercises, their brown fat converts the white-yellow fat into more brown fat, helping them burn calories and mold them into a healthier state, which is something obese people desperately need.

"Prior to our work, the only known way to activate human brown adipose tissue was through cold exposure," Cypess said. While inexpensive, this approach is generally not well tolerated over the long term, and there is significant variability in people's responses. In addition, once the cold exposure is removed, the effect usually turns off rather quickly."

Brown fat is also activated with cold temperatures; however, this is the first time researchers have discovered an alternative way to turn on the fat’s metabolizing engine. Researchers around the world are experimenting with this potentially powerful type of fat, with the belief it could be the answer to America’s obesity epidemic. With more than one-third of the country weighing in with an obese body mass index, according to the Centers for Disease Control and Prevention, solutions are in desperate demand. Obesity remains as one of the nation’s increasingly burdensome and life-threatening problems to date.

Source: Cypess A, Weiner LS, Roberts-Toler C, Elia EF, Kessler SH, and Kahn PA et al. Activation of Human Brown Adipose Tissue by a 3-Adrenergic Receptor Agonist. Cell Metabolism. 2014.