Brown fat has gained more notice in recent news, mostly for its ability to produce 300 times more heat than any other organ in your body. While ordinary white body fat (bad fat) piles on when we eat more calories than we burn, brown fat (good fat) generates heat, thusly burning that energy stored in white fat. Though brown fat is common in babies--it’s what keeps them warm--studies have found that we have a small amount in our necks, too.
In fact, sleeping in a cold bedroom could activate brown fat in adults, a U.S. study in the journal Diabetes found. In the study, five healthy young men slept in a climate-controlled bedroom for four months. In the first month, the room was kept at 74 degrees Fahrenheit, lowered to 66 degrees Fahrenheit in the second, brought back to 74 degrees Fahrenheit in the third, and raised to 80 degrees Fahrenheit in the fourth.
After the second month of sleeping at 66 degrees Fahrenheit, the men had almost doubled their volumes of brown fat. They burned more calories throughout the day—though not enough to lose weight—and their insulin sensitivity improved. Sleeping naked or in cooler temperatures (or both!) can help to activate brown fat, so this is really a no-brainer.