Fat: Brown Good, White Bad

It’s not generally known, but body fat comes in two colors – brown and white. It’s always been thought that brown fat existed only in humans during childhood, and was gone by the time we’re adults. Now scientists at the Joslin Diabetes Center, Boston, have demonstrated that brown fat not only exists in adults, but that it’s metabolically active. Their report (along with two others) is published in the New England Journal of Medicine.

The scientists examined the results of positron emission tomography/computed tomography (PET/CT) scans done on some 2,000 patients for different reasons. Brown fat deposits were seen in 7.5% of females and 3% of males. Not surprisingly, younger patients had more brown fat, and brown fat was found more readily in scans taken during cold weather, in people who were thin or were using beta-blocker drugs. People with a raised body mass index (BMI) and those over 64 were less likely to have brown fat. The PET data showed that the brown fat had high metabolic activity.

The importance of these findings lies in the fact that brown fat is active in burning calories and using energy. If one could find a way to stimulate brown fat growth it might be a valid approach to treating overweight and obesity, and possibly type 2 diabetes. Maybe we should encourage lower thermostat settings?