A drug used to treat overactive bladder can also boost calorie burning and aid in weight loss, a new study finds.

The study involved 15 men who have never used mirabegron prior to the study. They all underwent imaging scans to determine who among them had detectable amounts of brown fat. Brown fat helps burn calories and keeps the body warm.

Twelve participants were given 200 mg of mirabegron, higher than the 50 mg standard prescription. The researchers observed that the brown fat metabolic activity increased, which translated to 203 calories burned per day, or 11 pounds in a year.

"Brown adipose tissue, or brown fat, produces β3-adrenergic receptor at levels higher than nearly every other organ in the body. We showed that a one-time dose of the drug mirabegron stimulates human brown adipose tissue so that it consumes glucose and burns calories," lead author Dr. Aaron Cypess, head of the Diabetes, Endocrinology and Obesity Branch at the National Institute of Diabetes and Digestive and Kidney Diseases, said in a press release.

The findings of the study can be used to develop safe drugs that can help combat obesity, treat people with irregular metabolism and fatty liver disease.

The researchers admitted that further study is needed before mirabegron can be used for weight loss.

"We don't know if the drug is effective when taken chronically," Cypess said to LiveScience. "Since all drugs have side effects, it's not ethical for us to recommend its use for weight loss until we have more information on both efficacy and safety."

The study was published in the Jan. 12 issue of the Federation of American Societies for Experimental Biology.